I was so tired that I ____ when I was sitting in the armchair reading.

问题描述:

I was so tired that I ____ when I was sitting in the armchair reading.
A . dropped away
B . dropped out
C . dropped off
D . dropped through

哪个正确呢?请翻译,非常感谢

c 正确 这个短语的意思是睡着. 整句意思是 我是那么累以至于坐在沙发商读书时睡着了.