WHO精子活力分级,b级是指()
A.精子呈不动状态
B.精子呈缓慢或非前向运动
C.精子呈中速直线运动
D.精子呈高速直线运动
E.精子呈高速旋转运动
参考答案:C
This cake is very sweet. You _____ a lot of sugar in it. [ ]
A. should put
B. could have put
C. might put
D. must have put
汽缸勾贝即汽缸活塞,它在锅炉送来的蒸汽作用下,在汽缸内高速往复运动。