Question

Although the police thought he was the most likely one, _____ they had no exact proof about it, they could not arrest him.

A．when

B．until

C．before

D．since

Answer 1

D

考查连词.   A.当……时候B.直到…… C.在……以前    D.因为；由于；自……以来。句意：尽管警察认为他是最可能的一个，由于他们没有确切的证据，他们也不能逮捕他。选D。