大全 sec b-12---不解

12.
     Stars like the sun can continue to shine steadily for billions of years because its light and heat are produced by nuclear fusion, in which titanic releases of energy result in the loss of only tiny amounts of mass.

(A) its light and heat are produced by nuclear fusion, in which

(B) nuclear fusion produces its light and heat, in which

(C) nuclear fusion produces their light and heat, where

(D) its light and heat are produced by nuclear fusion, where（E）

(E) their light and heat are produced by nuclear fusion, in which

为什么ABD错，不能用单数 ？？？？

为什么ABD错，不能用单数 ？？？？

谢谢版主啊！  弱问：为什么不能指代sun呢....