轨道检查车、接触网检测车、电务试验车连挂速度有何要求？
参考答案：
连挂速度不超过3km/h。
—Now the air in our hometown is even ______ than it was before.
—So we must do something to stop it. [ ]
A. dirty
B. better
C. worse
D. more better
人们习惯把肌肉靠身体正中面或肢体近端的附着处称为（）。
A.定点
B.起点
C.近固点
D.动点
