题干
Many people do not realize the importance of health __________ they have fallen ill.
A：since
B：until
C：while
D：after
答案(点此获取答案解析）
B
Many people do not realize the importance of health __________ they have fallen ill.
A：since
B：until
C：while
D：after
Y是原子序数大于4的短周期元素，Xm+ 和Yn– 两种离子的核外电子排布相同，下列说法中正确的是
