Which of the following activities increases the yield of `C_3` plants?

Options

A. Increasing `CO_2` in atmosphere
B. Increasing `O_2` in atmosphere
C. Decreasing humidity in atmosphere
D. Decreasing temperature in atmosphere

Answer

To determine which activity increases the yield of C3 plants, we need to analyze the options provided:

1. **Increase in CO2 in atmosphere**: C3 plants utilize carbon dioxide (CO2) during photosynthesis. An increase in CO2 concentration enhances the rate of photosynthesis, leading to higher yields. Therefore, this option is likely to increase the yield of C3 plants.

2. **Increase in O2 in atmosphere**: C3 plants primarily take in CO2 and release O2 as a byproduct. An increase in O2 concentration does not directly benefit the yield of C3 plants and may even lead to photorespiration, which can be detrimental to their growth.

3. **Decrease in humidity in atmosphere**: Lower humidity can lead to increased transpiration rates in plants, which may stress them and potentially reduce their yield. Therefore, this option is not likely to increase the yield of C3 plants.

4. **Decrease in temperature in atmosphere**: C3 plants generally prefer moderate temperatures for optimal photosynthesis. A decrease in temperature could slow down metabolic processes, potentially reducing yields, especially if temperatures drop too low.

Based on this analysis, the activity that increases the yield of C3 plants is:

**Answer: Increase in CO2 in atmosphere.**

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