下列物质露置在潮湿的空气中一段时间后，质量不会增加的是（  ）

Boys and girls,

Attention, please! Do you know 1to keep safe in our daily（日常的）life? Today I’d like2 you some ways to keep safe.

1  Always play in a 3 place. A park is a safe place4 there are no cars or buses in it.

2  5 the traffic rules, please! Before crossing a road,6 and look both ways ——look left, look right and look left 7.

3  Never put your head or hands 8 a car, a bus or a train. Many people get 9 or lose their lives by doing so.

4  Don’t 10 a stranger（陌生人）or go with him/her.

That’s all. All the students should obey the rules anytime(任何时候).

生活中，他尽可能多地承担家务事。每天饭后，争着洗碗；写完了作业，他会帮母亲按按背，捶捶脚。周末一到，他将洗衣服、拖地等全部揽下。学习上，王震宇格外努力，成绩总是名列前茅。