CRTSⅠ型轨道板封锚砂浆应分层填压，采用（）进行振捣。
A、人工
B、振捣棒
C、附着式振动器
D、空气锤
参考答案：D
-----Who helped ________with the job ?
-----Nobody , They did it by______.
A．them, them
B．them, themselves
C．themselves, them
D．themselves, themselves
跨国制作
