885 section 4 23

A huge flying reptile that died out with the dinosaurs some 65 million years ago, the Quetzalcoatlus had a wingspan of 36 feet, believed to be the largest flying creature the world has ever seen.

(A) believed to be

(B) and that is believed to be

(C) and it is believed to have been

(D) which was, it is believed,（C）

(E) which is believed to be

我是这样理解的带红线的可以看作是同位语,如果选c的话,have修饰Quetzalcoatlus,如果这个词是单数(后面有it),那这里不是应用has,请解释下