TOEFL Reading: ETS-TOEFL阅读机经 - DM82239ZGC6OA3W0L$

Why does the author provide the information that "The closed canopy blocks light to the ground" A. To illustrate why rodents living in tropical forests live in social groups B. To illustrate why tropical forests have so many species of bats C. To explain why there are few mammals that live on the ground D. To explain why some species of monkeys do very well in the tropics