WHO推荐检测精子密度和活动率的方法为()。
A.计算机辅助精子分析
B.普通光学显微镜直接目测法
C.精子运动轨迹图像分析法
D.精子分析仪法
E.相差显微镜检测法
参考答案:B
Some passengers were walking through one of the big halls at
De Gaulle Airport _____ the whole roof (屋顶) fell down. [ ]
A. while
B. as soon as
C. when
D. after
复线上在距道口不少于7m范围内,应能看到两侧各()以外的列车。
A.400m
B.500m
C.600m
D.300m