Assertion(A): The Ozone layer present at the top of stratosphere is very crucial for human survival.
Reason (R): Ozone layer prevents IR radiation.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true and R is NOT the correct explanation of A.
C. A is true but R is false
D. A is false and R is true

Explanation

To solve the given assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Analyze the Assertion (A)
The assertion states that "The Ozone layer present at the top of stratosphere is very crucial for human survival."

- The ozone layer is indeed located in the stratosphere, approximately 10 to 30 miles above the Earth's surface.
- It plays a vital role in protecting living organisms by absorbing the majority of the sun's harmful ultraviolet (UV) radiation.

**Conclusion for Step 1:** The assertion is true.

### Step 2: Analyze the Reason (R)
The reason states that "Ozone layer prevents IR radiation."

- Infrared (IR) radiation is a type of electromagnetic radiation, but the ozone layer primarily absorbs UV radiation, not IR radiation.
- The ozone layer is effective in filtering out UV rays, which can cause skin cancer and other harmful effects on living organisms.

**Conclusion for Step 2:** The reason is false.

### Step 3: Determine the Relationship Between A and R
Now, we need to determine the relationship between the assertion and the reason.

- Since the assertion is true and the reason is false, the correct relationship is that the assertion stands independently as true, while the reason does not support it.

### Final Conclusion
Based on the analysis:
- Assertion (A) is true.
- Reason (R) is false.
- Therefore, the correct answer is that A is true and R is false.