问题补充：
Why do we go to bed ?
答案：
如果没有上下文,可以有若干答案.
如：Because we e tired.
Because we e sleepy.
Because its too late.
Because Mom makes us go to bed.
Because we need to have enough rest.
======以下答案可供参考======
供参考答案1:
becuse we are sleeping
供参考答案2:
because we need rest.
供参考答案3:
Its too early now
供参考答案4:
because we are too tired!
供参考答案5:
because we have to sleep to keep fit
