题目内容：

根据句意，用括号内所给单词的适当形式填空。

1.It is clear that most of the ___________ (tourist) bags are full of souvenirs.

2.After a night’s work without sleep, he looked very ___________ ( sleep).

3.More and more people have realized the ___________ (important) of wetlands.

4.The old man looked __________ (sad) at his grandson with tears in his eyes.