根据句子意思，用括号内所给单词的适当形式填空。 小题1:The plane ha

问题：

根据句子意思，用括号内所给单词的适当形式填空。

小题1:The plane hasn’t arrived yet. Do you know the time of its_____ (arrive)?

小题2:Mr. Sun felt cold and _________ ( frighten).

小题3:_________(luck), I got full marks in the last exam.

小题4:You needn’t take a notebook with you if you find it __________ (necessary).

小题5:Many people don’t know the _________ (important) of the wetlands.