OG11-89 关于假设题的“对选项取非”

Networks of blood vessles in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.

89. The argument in the passage relies on which of the following assumptions?

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.

把这个选项取非应该怎么取阿?

是说"if these networks were useful, then a sandactylus would have had networks"

还是说“即使useful, sandactylus也不会有network”阿

因为根据Lawyer的解题方法，将选项取非后则原文必不对，

那么这个选项A是怎么做到的...

谢谢了~~