题干
. Be careful when you cross this very busy street. If not, you may _______ run over by a car.
A：have
B：get
C：become
D：tur
答案(点此获取答案解析）
B
A：have
B：get
C：become
D：tur
衰变成钋核
并放出一个粒子，其半衰期为
天，
氡经过
天衰变掉氡核的质量以及