I didn’t know which bag was better than the other, so I took them________.

A．each

B．either

C．both

D．none

可以阻止病毒自局部粘膜入侵的免疫因素是

A．月经周期缩短，基础体温双相
B．月经周期正常，但经期延长，基础体温双相
C．月经周期不规则，经量增多，基础体温单相
D．月经周期不规则，经量减少，呈点滴状
E．月经规则，经量无改变