— Did you find the missing couple in the mountain yesterday?

— No, but we________to get in touch with them ever since. [ ]

A. have tried  

B. have been trying

C. had tried  

D. had been trying

秦朝开始使用的“皇帝”称号和夏、商、周的“王”称号相比，本质的不同是（）

A.具有神化君权的特点

B.代表至高无上的权力

C.是古代政治发展的产物

D.是封建专制主义中央集权制度建立的表现