_________（50）A.Humans have no direct perception o

_________（50）

A.Humans have no direct perception of infrared rays.

B.In the dense complex world of a tropical forest,it is more important to see well than to develop an acute sense of smell.

C.That gives the eye a wilder view.

D.The red flag is black to the bull.

E.There are different mammals in tropical forest.

F. In this world,objects glowed with varying degrees of intensity.