2011年3月11日13:46日本发生了震惊世界的大地震，近期国际机构将日本核电事故等级上调至国际核能事件分级表(INES)中最严重的7级，据估算其向大气排放的放射性物质量约为630000太贝克，用科学记数法表示为： （  ）

阅读短文，并完成小题。

    It is said that more than four million people die each year from smoking. The number is frightening.

    Yet people around the world continue to smoke. In the USA, about forty-seven-million adults smoke. This year, more than 430,000 Americans died of diseases which have something to do with smoking. The American Cancer Society (美国癌症协会) says smoking harms the body greatly. It warns that smoking even a number of cigarettes is dangerous.

    戒烟是不容易的 However, doctors say you probably will live longer if you do stop smoking. You will feel better and look better. You also will protect the health of family member who breathe your smoke.

    There is not one right way to stop smoking, doctors say. Anyway can help. You can take long walks or spend time in places where smoking is not allowed. Also, you can eat a small piece of fruit or vegetable instead of having a cigarette. The sooner you stop smoking, the more you'll reduce(减少) your chances of getting cancer and other diseases.

    Stop smoking before smoking stops you!