I think Lisa _____ in the library.[ ]
A. maybe
B. may be
C. may is
D. is maybe
答案:B
绒毛膜促性腺激素何时出现分泌高峰
A.受精后10天
B.妊娠10~12周
C.受精后12天
D.妊娠5~7周
E.妊娠8~10周
航向CSB信号的方向性图在跑道中心延长线方向为最大值。