根据句意和汉语注释，在答题卡标有题号的横线上，写出单词的正确形式。

根据句意和汉语注释，在答题卡标有题号的横线上，写出单词的正确形式。
小题1:Everybody knows people and animals need clean air to ___________(呼吸).
小题2:Have you heard of the early ___________(移居者)problems on Mars.
小题3:There are __________ (各种各样的) designs of shoes for shoppers to choose from.
小题4:One of the __________(缺点) of living in Singapore is that we are not used to the food there.