Yesterday it rained heavily when school was over. We _______ stay in our classroom. [ ]

A. must

B. should

C. had to

D. need

生育年龄的妇女，血中雌激素分泌的第一个高峰是在

A．月经中

B．月经周期第一周

C．月经周期第21天

D．排卵前1天

E．排卵后11天