It is suggested that all these gifts be mailed immediately _________ in time for Christmas.

A．in order to have received

B．so as to receive

C．so as to be received

D．so as to be receiving

煤工作面煤壁到末排支柱（）的距离叫控顶距。

A、顶梁处

B、顶梁后端

C、或切顶柱