[讨论]prep 20

搜了以前讨论的 内容很少还是没有理解

The hognose snake puts on an impressive bluff, hissing and rearing back, broadens the flesh behind its head the way a cobra does, feigning repeated strikes, but, having no dangerous fangs and no venom, eventually, if its pursuer is not cowed by the performance, will fall over and play dead.

(A) broadens the flesh behind its head the way a cobra does, feigning repeated strikes, but, having no dangerous fangs and no venom,
(B) broadens the flesh behind its head the way a cobra does and feigns repeated strikes, but with no dangerous fangs and no venom,
(C) broadening the flesh behind its head the way a cobra does and feigning repeated strikes, but it has no dangerous fangs and no venom, and
(D) broadening the flesh behind its head the way a cobra does and feigns repeated strikes, but with no dangerous fangs and no venom, and
(E) broadening the flesh behind its head the way a cobra does, feigning repeated strikes, but with no dangerous fangs and no venom, and

C选项中的 but it has no dangerous fangs and no venom, and eventually, if.....,will fall over...

If....是插入语可以理解 可是为什么and前面还要逗号呢？有点印象还有一道题也是这样的结构。这个结构为什么，and 后面加谓语 不是完整句子呢