In the Tianjin fire accident, so many brave soldiers died for saving people _______ we know where our power is from.

A. who           B. that          C. as

请问这道题为什么选 B，还有就是这个句子怎么翻译，where 开始是什么从句，怎么翻译？谢谢老师。

以上句子结构为：

(1) so ...that..引导的结果状语从句( 意思是“如此…(以致…);到…的程度(以致…): 

(2) where our power is from 是连词副where词引导的宾语从句，作动词 know。

so...that 引导结果状语从句的例如如下

The tears were streaming so fast she could not see.

眼泪哗哗地流下来，她的视线一下子就模糊了。

The deal seems so attractive it would be ridiculous to say no.

这笔交易看上去太诱人了，要是拒绝它简直是笑话。

Frescoes are so familiar a feature of Italian churches that it is easy to take them for granted.

壁画在意大利教堂里是司空见惯的，以至于人们往往会视而不见。

He's not so daft as to listen to rumours. 

他没那么蠢，不会听信谣言的。