题目内容：

根据句子意思，用括号内所给词的适当形式填空。

1.The book with a blue cover is one of the __________ (twin).

2.At the end of that cold winter day, they __________ (decide) to go for a walk after dinner to relax.

3.I finished my Math homework an hour ago, but I forgot __________ (write) my English homework.

4.There is nothing wrong with __________ (keep) a snake if you like.

5.These __________ (video) are made by some students as a gift for their teachers.