— 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

船舶载重线证书的有效期届满后进行的检验属于（）

A.船级检验

B.保持船级检验

C.法定检验

D.特别检验