粗死亡率
参考答案：
死亡总人数与该人群同期平均人口数之比。
—We'd better hurry; we'll be late.
— __________. Do you really want to listen to the boring lecture?
A．For what?
B．Take it easy.
C．What on?
D．So what?
太阳与地球之间的距离约为一亿五千万千米，这个数写作______千米，改写成以“亿”作单位的数是______千米．
