Question

So nervous_____that she ran back to her seat when she was going to give her speech before other.

A she was B was she C she had been Dhad she been为什么用B，不用D

Answer 1

当她要去在别人面前演讲时，她是如此紧张，以至于跑回她的座位上去了。本句强调其紧张，故将so nervous 提前，还原后为she was so nervous that she ran back to her seat when...,when后为时间状语表过去，前因后果，so that 表因果条件从句，前后状态一致。所以选B。，还有啊，nervous是心情词，表示过去紧张时，只会说I was nervous，而不会用过去完成时的

Answer 2

你好 ！如果没有最佳选择，如果是平时随意写个句子，用had she been也能说得过去，只是浪费笔墨而已。但本复合句除了when引导的过去将来时，表示的都是过去一般状态，所以没必要用过去完成时态。

Answer 3

因为有When