The large number of physiological and behavioral similarities between birds and mammals, which have separate evolutionary histories, are generally attributed to endothermy.

　　假设这是这篇文章的核心观点，那么我问下面这个问题：

　　The passage suggests which of the following about endothermy?

　　A. it is a common cause of many similarities between birds and mammals

　　B. it is regarded as a cause of many similarities between birds and mammals

　　A选项中，endothermy是鸟与兽相似的原因，而B则表示endothermy被认为是鸟与兽相似的原因。我们回归原文，主要看的是are generally attributed to…这里的被动体现的就是视角问题。这里表达的是endo是被别人认为是，但并不代表作者认为是。因此此处应该选B。这就是视角问题。