They _________ on the program for almost one week before I joined them, and now we are still working on it as no good results have come out so far.

A．have worked

B．had worked

C．have been working

D．had been working

港澳通行证的有效期为（），持证人在办理签注时如证件有效期不足（），可申请换发。

A.3年，3个月

B.3年，6个月

C.5年，3个月

D.5年，6个月