Question

David,turn off the TV ___ no one is watching it. But it ____ off already!

David,turn off the TV ___ no one is watching it.
But it ____ off already! The music is from the radio.
A so that, has been turned B when , has turned
C if , has been turned D because , has turned
为什么不选B,D

Answer 1

正确：C
结合句意得知第一空应该填if(如果）更为准确。又第二空的主语it=the TV, 存在被动语态，B和D的has turned是主动结构，故排除它们。

Answer 2

这是一组对话
A：David，如果没人看电视就把电视关了
B：电视已经关了！声音是收音机发出来的。
由B的话可以知道A不知道声音是从哪里发出的，所以可能并不能看到有没有人看电视（或许不在电视的房间），所以用If，表如果。
可以感觉一下，其他选项都不合适。

Answer 3

因为这里电视被关掉是被动的。TV has been turned off，所以BD就选不了了。

Answer 4

David,turn off the TV ___ no one is watching it.
But it ____ off already! The music is from the radio.
A so that, has been turned B when , has turned
C if , has been turned D because , has turned
选项是C.
因为选项B和D的第二空不是被动形式。

Answer 5

because has turned