[求助]885 SEC C-15

15.   Astronomers studying the newly discovered star say that it provides clues about our galaxy’s origin, that it may supply data about how fast our galaxy is expanding, and moreover it is perhaps the most distant star in the entire Milky Way.

(A) about how fast our galaxy is expanding, and moreover it is perhaps

(B) regarding the speed our galaxy expands at; moreover, they think it may be

(C) about how fast our galaxy expands and perhaps be

(D) on the galaxy’s expansion rate and perhaps（E）

(E) about how fast our galaxy is expanding, and that it is perhaps

答案是E，为什么不选A？E中的that 指代什么？