求助~~~

1.        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,

(E) which is believed to be

为什么A不行呢？答案反正是C，那从那看出来要用现在完成时呢?