(A)          Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.

(B)          All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.

(C)          Winged dinosaurs that flapped their wings

t ,, in flight would have been able to fly more effectively than winged dinosaurs that could only glide.

(D)          If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.

(E)          Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

本题不解为何选A，请ｎｎ帮忙解释一下！！

A is right,

Look at the bold-faced words below:

"Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings."  That means that the only use of the networks of blood vessels is for fly. Now the dinosaur Sandactylus had the same kind of network, what do you think? A answers the question.

在bat's的血管系统的出现是为了散热，热是由于扑腾翅膀

在Sandactylus 恐龙的翅膀里也有类似的血管系统，所以Sandactylus 这种恐龙是扑腾翅膀的，不是滑翔的

问：assumption

A：如果这样的血管系统没用是不会出现的。－－－血管就是用来散热的，散扑腾翅膀产生的热

B：所有的扑腾翅膀的动物都有这样的血管系统。－－－现在还不知道Sandactylus 是不是扑腾翅膀

C：讲Sandactylus的飞行和滑行，没有提到血管

D:： 发现Sandactylus飞行的证据，还是无关

E：同B现在还不知道Sandactylus 是不是扑腾翅膀，需要建立assumption才能成立

这里的assumption有点加强的做法