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[A]: Light is very important external fa...

[A]: Light is very important external factor of transpiration.
[R]: Light induces stomata! opening and darkness stomata! closure. Thus the rate of transpiration increases in light and de- creases in dark.

A

If both A and R are true and R is the correct explanation of A

B

If both A and R are true but R is not the correct explanation of A

C

If A is true and R is false

D

If both A and R are false

Text Solution

AI Generated Solution

The correct Answer is:
### Step-by-Step Solution: 1. **Understanding the Assertion**: The assertion states that "light is a very important external factor of transpiration." This means that light plays a significant role in the process of transpiration in plants. 2. **Understanding the Reason**: The reason provided is that "light induces stomatal opening and darkness causes stomatal closure." This indicates that the presence of light affects the behavior of stomata, which are small openings on the leaves of plants. 3. **Analyzing the Effects of Light and Darkness**: - **In Light**: When light is present, stomata open, allowing water vapor to escape from the plant, which increases the rate of transpiration. - **In Darkness**: Conversely, in the absence of light, stomata tend to close, reducing the rate of transpiration. 4. **Connecting Assertion and Reason**: Since the assertion claims that light is important for transpiration and the reason explains how light affects stomatal behavior (opening in light and closing in darkness), we can see that the reason supports the assertion. 5. **Conclusion**: Both the assertion and the reason are true, and the reason correctly explains why light is an important factor in transpiration. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion. ### Final Answer: Both assertion and reason are true, and reason is the correct explanation of the assertion. ---
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Knowledge Check

  • Dark Snow Most of Greenland’s interior is covered by a thick layer of ice and compressed snow known as the Greenland Ice Sheet. The size of the ice sheet fluctuates seasonally: in summer, average daily high temperatures in Greenland can rise to slightly above 50 degrees Fahrenheit, partially melting the ice, in the winter, the sheet thickens as additional snow falls, and average daily low temperatures can drop to (12) ul("as low as 20 degrees") . Typically, the ice sheet begins to show evidence of thawing in late (13) ul("summer. This follows") several weeks of higher temperatures. 14 ul("For example") , in the summer of 2012, virtually the entire Greenland Ice Sheet underwent thawing at or near its surface by mid-July, the earliest date on record. Most scientists looking for the causes of the Great Melt of 2012 have focused exclusively on rising temperatures. The summer of 2012 was the warmest in 170 years, records show. But Jason (15) ul("Box, an associate") professor of geology at Ohio State believes that another factor added to the early (16) ("thaw") , the “dark snow” problem. According to Box, a leading Greenland expert, tundra fires in 2012 from as far away as North America produced great amounts of soot, some (17) ul("of it") drifted over Greenland in giant plumes of smoke and then (18) ul("fell") as particles onto the ice sheet. Scientists have long known that soot particles facilitate melting by darkening snow and ice, limiting (19) ul("it’s") ability to reflect the Sun’s rays. As Box explains, “Soot is an extremely powerful light absorber. It settles over the ice and captures the Sun’s heat.” The result is a self-reinforcing cycle. As the ice melts, the land and water under the ice become exposed, and since land and water are darker than snow, the surface absorbs even more heat, which (20) ul("is related to the rising temperatures") . [1] Box’s research is important because the fires of 2012 may not be a one-time phenomenon. [2] According to scientists, rising Arctic temperatures are making northern latitudes greener and thus more fire prone.[3] The pattern Box observed in 2012 may repeat (21) ul("itself again") , with harmful effects on the Arctic ecosystem. [4] Box is currently organizing an expedition to gather this crucial information. [5] The next step for Box and his team is to travel to Greenland to perform direct sampling of the ice in order to determine just how much the soot is contributing to the melting of the ice sheet. [6] Members of the public will be able to track his team’s progress—and even help fund the expedition—through a website Box has created. (22)

    A
    NO CHANGE
    B
    falls
    C
    will fall
    D
    had fallen

  • Dark Snow Most of Greenland’s interior is covered by a thick layer of ice and compressed snow known as the Greenland Ice Sheet. The size of the ice sheet fluctuates seasonally: in summer, average daily high temperatures in Greenland can rise to slightly above 50 degrees Fahrenheit, partially melting the ice, in the winter, the sheet thickens as additional snow falls, and average daily low temperatures can drop to (12) ul("as low as 20 degrees") . Typically, the ice sheet begins to show evidence of thawing in late (13) ul("summer. This follows") several weeks of higher temperatures. 14 ul("For example") , in the summer of 2012, virtually the entire Greenland Ice Sheet underwent thawing at or near its surface by mid-July, the earliest date on record. Most scientists looking for the causes of the Great Melt of 2012 have focused exclusively on rising temperatures. The summer of 2012 was the warmest in 170 years, records show. But Jason (15) ul("Box, an associate") professor of geology at Ohio State believes that another factor added to the early (16) ("thaw") , the “dark snow” problem. According to Box, a leading Greenland expert, tundra fires in 2012 from as far away as North America produced great amounts of soot, some (17) ul("of it") drifted over Greenland in giant plumes of smoke and then (18) ul("fell") as particles onto the ice sheet. Scientists have long known that soot particles facilitate melting by darkening snow and ice, limiting (19) ul("it’s") ability to reflect the Sun’s rays. As Box explains, “Soot is an extremely powerful light absorber. It settles over the ice and captures the Sun’s heat.” The result is a self-reinforcing cycle. As the ice melts, the land and water under the ice become exposed, and since land and water are darker than snow, the surface absorbs even more heat, which (20) ul("is related to the rising temperatures") . [1] Box’s research is important because the fires of 2012 may not be a one-time phenomenon. [2] According to scientists, rising Arctic temperatures are making northern latitudes greener and thus more fire prone.[3] The pattern Box observed in 2012 may repeat (21) ul("itself again") , with harmful effects on the Arctic ecosystem. [4] Box is currently organizing an expedition to gather this crucial information. [5] The next step for Box and his team is to travel to Greenland to perform direct sampling of the ice in order to determine just how much the soot is contributing to the melting of the ice sheet. [6] Members of the public will be able to track his team’s progress—and even help fund the expedition—through a website Box has created. (22)

    A
    NO CHANGE
    B
    soot
    C
    of which
    D
    DELETE the underlined portion.

  • Dark Snow Most of Greenland’s interior is covered by a thick layer of ice and compressed snow known as the Greenland Ice Sheet. The size of the ice sheet fluctuates seasonally: in summer, average daily high temperatures in Greenland can rise to slightly above 50 degrees Fahrenheit, partially melting the ice, in the winter, the sheet thickens as additional snow falls, and average daily low temperatures can drop to (12) ul("as low as 20 degrees") . Typically, the ice sheet begins to show evidence of thawing in late (13) ul("summer. This follows") several weeks of higher temperatures. 14 ul("For example") , in the summer of 2012, virtually the entire Greenland Ice Sheet underwent thawing at or near its surface by mid-July, the earliest date on record. Most scientists looking for the causes of the Great Melt of 2012 have focused exclusively on rising temperatures. The summer of 2012 was the warmest in 170 years, records show. But Jason (15) ul("Box, an associate") professor of geology at Ohio State believes that another factor added to the early (16) ("thaw") , the “dark snow” problem. According to Box, a leading Greenland expert, tundra fires in 2012 from as far away as North America produced great amounts of soot, some (17) ul("of it") drifted over Greenland in giant plumes of smoke and then (18) ul("fell") as particles onto the ice sheet. Scientists have long known that soot particles facilitate melting by darkening snow and ice, limiting (19) ul("it’s") ability to reflect the Sun’s rays. As Box explains, “Soot is an extremely powerful light absorber. It settles over the ice and captures the Sun’s heat.” The result is a self-reinforcing cycle. As the ice melts, the land and water under the ice become exposed, and since land and water are darker than snow, the surface absorbs even more heat, which (20) ul("is related to the rising temperatures") . [1] Box’s research is important because the fires of 2012 may not be a one-time phenomenon. [2] According to scientists, rising Arctic temperatures are making northern latitudes greener and thus more fire prone.[3] The pattern Box observed in 2012 may repeat (21) ul("itself again") , with harmful effects on the Arctic ecosystem. [4] Box is currently organizing an expedition to gather this crucial information. [5] The next step for Box and his team is to travel to Greenland to perform direct sampling of the ice in order to determine just how much the soot is contributing to the melting of the ice sheet. [6] Members of the public will be able to track his team’s progress—and even help fund the expedition—through a website Box has created. (22) 13. Which choice most effectively combines the two sentences at the underlined portion?

    A
    summer, following
    B
    summer, and this thawing follows
    C
    summer, and such thawing follows
    D
    summer and this evidence follows

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