根据句意，在答卷标有题号的横线上，写出括号内所给单词的适当形式。

根据句意，在答卷标有题号的横线上，写出括号内所给单词的适当形式。
小题1:They are planning when and where to celebrate his grandfather’s _____(ninety) birthday.
小题2:‘Nanjing! Nanjing!’ is a film full of _____(sad). All of us felt depressed after seeing it.
小题3:The weather in the north is much _________(dry) than that in the south.
小题4:The world _______(it) is changing all the time.