选词填空：选择方框里的单词或词组并用其恰当形式填空，使句子完整，句意通顺。ast

1. — Put that bag in its _____ place, and we can find it easily next time.
     — Oh, I will do it at once.
2. — What a special bridge it is!
    — Yes. It ________ lots of huge stones.
3. — Why do we use a ________ bag to go shopping?
    — Because it can reduce pollution.
4. — How many _____ were there in Shen Zhou Ⅶ? 
    — Three.
5. — Why should we plant more trees?
    — Because the trees can _____water from washing the earth away.