一袋奶粉重500克，4袋奶粉重（   ）。

下列词语书写无误的一项是（    ）

在一个雷雨交加的夜晚，小爽正在家里窗台下做作业，但他打开窗户向外望去…请你设想一下

（1）他可能会看到什么？听到什么？还有一个什么疑问？（提出一个与物理有关问题不用回答）

（2）小爽记得光在真空中的速度是C=3.0×10⁸m/s，声音在空气中的传播速度是V=340m/s，于是，他想探测打雷处距离他有多远？他动了动脑筋，用自己的电子手表测出了看到闪电后经过t=2s钟便听到雷声的时间，而后算了算，结果就出来了．请你粗略地将他的计算过程及结果写出来．

    There are a lot of Chinese cultures about fish. In Chinese, “fish” sounds like “surplus”（余），Chinese people always like to have a surplus at the end of the year. They think if they save something at the end of the year, then they can make more in the next year. That's why Chinese people like to eat fish for the New Year. Do you know what kind of fish Chinese people like to eat for the New Year?

Crucian carp

    The first kind of fish is crucian carp. It sounds like the Chinese word“吉”. The Chinese word mean “good luck”. Chinese people think that eating crucian carp can bring good luck for the next year.

Chinese mud carp

    The second kind of fish is Chinese mud cap. It sounds like the Chinese word“礼”. It means gifts or presents. So, Chinese people choose to eat Chinese mud carp during the Chinese New Year. It means “good future”.

Catfish

    The third kind of fish is catfish. It sounds like two Chinese words “年余”.So eating catfish is a wish for a surplus in the New Year.