题目内容：

根据句意，用括号内所给单词的适当形式填空。

1.We are so lucky to live in the _________ (social) like this.

2.The advertisement seems _________ (humour)， but its message is not a joke.

3.I had to get one at the bookshop since they _________ (sell) so well.

4.The girl is in poor health. She gets tired _________ (easy).