Answer: (Detailed Solution Below)
Option A: Both A and R are true and R is the correct explanation of A
Detailed Solution:
The correct answer is “Both A and R are true and R is the correct explanation of A”.
Insolation is the primary energy input for the biosphere. It's the solar radiation that reaches the Earth's surface. Green plants are the primary producers in the ecosystem. They convert solar energy (insolation) into chemical energy (food) through photosynthesis.