Assertion : Food chains generally consist of more than four trophic levels.
Reason : There is loss of energy at each trophic level and very little usable energy remains after four trophic levels.
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