牛睾丸长轴与地面（）。
A.平行
B.垂直
C.成一定角度
D.交叉
E.以上都不是
参考答案：B
The government is asked to improve school bus safety, ______? [ ]
A. didn't it
B. hasn't it
C. isn't it
D. doesn't it
观察法，按事先是否确定具体观察项目，可分为（）.
