一个有理数由符号和绝对值两部分组成，进行加法运算时，应注意：

首先判断两个加数的（    ）是同号还是异号，确定用哪条法则。然后确定和的符号，再确定绝对值的大小，最后将绝对值（    ）。

用所给词的正确形式完成短文。

(walk   they   take   make   light   candle   bad)

      Our environment is getting 1 ______ than before. Now more and more people realize that we should

do something to help the Earth. Here are the things we can do to help the Earth: We can recycle glass, metal

and paper. We shouldn't throw 2 ______ in the garbage can (垃圾箱)! We can 3 ______ instead of

driving cars! We should try to 4 ______ short showers and turn off all the 5 ______ and the TV

when we leave the room. All of these things will help the Earth.

1.______ 2.______ 3.______ 4.______ 5.______