35.

In laboratory rats, a low dose of aspirinusually suffices to block production of thromboxane,

which is a substance that promotes bloodclotting, but not seriously interfering with the

production of prostacyclin, whichprevents clotting.

(A) which is a substance that promotesblood clotting, but not seriously interfering

(B) a substance that promotes bloodclotting, but not seriously interfering

(C) a substance that promotes bloodclotting, but does not seriously interfere

(D) which is a substance to promote bloodclotting, but does not seriously interfere

(E) which is a substance that promotesblood clotting, but not a serious interference

Prep07语法笔记说:

(C)  正确, a substance that…同位语结构，作为thromboxane的同位语对thromboxane进行解释

说明; but does跳过同位语和suffices并列共同作为a low dose of aspirin的谓语动词

(D) but does…更像是跟is a substance…并列,从而作为了thromboxane的谓语动词,改变了原句

的意思

可以理解D说更像和is a substance并列，但是，为什么C中but does就跳过同位语和suffices并列了呢？在我看来，非常像和 that promotes并列了啊。

还有一个问题，but作并列的时候，是不是和and类似？这里如果but后能够有指代主句主语的代词it，我觉得才像是和主句并列啊...

求指教！谢谢