Assertion (A):The average temperature of the Earth has been rising. Reason (R):The greenhouse effect traps the Sun's heat within the Earth's atmosphere.

• A. Both (A) and (R) are true, and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
• C. (A) is true, but (R) is false.
• D. (A) is false, but (R) is true.
• E. Both (A) and (R) are false.