纵向受力钢筋为420和22且直接承受动力荷载的构件，采用机械连接的，按规定在700mm的接头区段内，不能同时有接头的是（）。

A．2根直径20mm和1根直径12mm钢筋

B．3根直径20mm钢筋

C．1根直径20mm和2根直径12mm钢筋

D．2根直径20mm钢筋

This reflects the priority being attached to economic over political activity, partly caused by a growing reluctance to enter a calling blighted by relentless publicity that all too often ends in destroying careers and reputations.

A．divine summons

B．political career

C．profession

D．business transaction