Man can hardly understand why many animals live their whole life in the desert, as  

A. water is an essential part of his existence

B. very few large animals are found in the desert

C. sources of flowing water are rare in a desert

D. water composes the greater part of the tissues of living things

Thông tin: Since water is the basis of life […]And since man’s inexorable necessity is to absorb large quantities of water at frequent intervals, he can scarcely comprehend that many creatures of the desert pass their entire lives without a single drop.