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

考查連詞.   A.當……時候B.直到…… C.在……以前    D.因為；由于；自……以來。句意：盡管警察認為他是最可能的一個，由于他們沒有確切的證據(jù)，他們也不能逮捕他。選D。