Assertion (A): Insolation is the most important source of energy for the biospheric ecosystem.
Reason (R): Solar radiation is converted into food and chemical energy by green plants.

Codes:

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 the correct explanation of A

C) A is true but R is false

D) A is false but R is true

This MCQ is part of the UP PSC Previous Year Questions (PYQs) series, focusing on UPPSC Prelims 1999 (GS Paper I)