在下列各句的空白处填入一个最恰当的单词，使句子意思完整，语法正确。

1.  The two boys look very_______. Maybe they are twins.

2.  When my bike doesn't work, my father can______it.

3.  We will think up some_______to solve the problem.

4.  Could you please hand these books_______? We'll use them in class.

5.  I think Uncle Zhang can help_______up the watch.