题目

Running is becoming popular these days, it is free. Many people do not have enough time to play a team sport, so instead they have started going running. In the past, running in the street was seen as a bit silly. But things are changing.【1】. Some people go to lose weight while others go simply to keep fit. Even at 6 o’clock in the morning you sometimes see runners in the streets. Scientists say that running is a very good way to keep fit.【2】. In some schools when it rains and it’s too wet to play football, children have to do cross country running instead. Now as running has becom受精的鸟卵在雌鸟体内开始发育，但鸟卵产出后就暂停发育，原因是外界（ ）A．温度太低B．温度太高C．具有空气D．具有阳光