885-5-9, thanks

windcolour

Astronomers at the Palomar Observatory have discovered a distant supernova explosion, one that they believe is a type previously unknown to science.

(A) that they believe is

(B) that they believe it to be

(C) they believe that it is of

(D) they believe that is（E）

(E) they believe to be of

can someone explain why E is the key?

gonghao

one和that意思重复

AB去掉

C：believe that it非常罗嗦，且和前面的one重复

D：that有指代one的意思，造成重复，that多余