液压牵引采煤机和电牵引采煤机都能实现无级调速。
参考答案：对
The library's study room is full of students _______ for the exam.
A．busily prepared
B．busy preparing
C．busyly prepare
D．are busily preparing
肺阴亏耗之咳嗽，其治法为（）
A．清热润燥，养肺生津
B．清热解毒，利尿通淋
C．滋阴补肾，理气通络
D．滋阴润肺，止咳化痰
