Question

At each end of the tube ________,one which gathers light and

Answer 1

原句应该是：

There are two lenses at each end of the tube, one which gathers light and one which magnifies the image.

管子的两端各有一个棱镜,一个聚光,一个放大.

倒装以后,应该是：

At each end of the tube (there) are two lenses, ...

其中there可以省略,就是答案D了.