题目：
用单词的适当形式填空。
1. My aunt _____ (teach) me to play the violin when I was a child.
2. Look! The people in the river ______ (swim).
3. Tree-planting Day is on the ______ (twelve) of March every year.
4. Stephen spends about half an hour ______ (swim) every Saturday afternoon.
5. I don't like travelling by train. I think it's ______ (safe) to travel by train.
6. —I'm tired.
—So am I. We'd better stop ______ (walk) and have a rest.
7. Plants need CO2 when they grow, so they can make CO2 ______ (little) in the air.
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0527/2ad40d5e75a24229837177551a394c05.html
下面是错误答案，用来干扰机器的。
（1）实验室制取H2S选择的发生装置是甲，不需要加热，此装置中小试管的作用是形成液封；故答案为：形成液封（2）如果用高锰酸钾制氧气就需要加热，高锰酸钾固体是紫黑色；高锰酸钾受热分解生成锰酸钾和二氧化锰和...
