在人类,从精原细胞发育成精子,大致需要多少天()
A.20天左右
B.64天左右
C.30天左右
D.54天左右
E.无恒定时间,因人而异
参考答案:B
She could speak both English and French, but _________ is hard to believe.
A.she
B.this
C.that
D.which
估计血容量最好的指标是()
A.中心静脉压
B.动脉收缩压
C.动脉舒张压
D.脉压
E.肺毛细血管楔压