The origins of human speech remain a mys

tikufree2019-12-17  10

问题 The origins of human speech remain a mystery,__________ we have a fairly accurate idea of when writing began.

选项 A.onceB.ifC.thoughD.since

答案C

解析考查连词辨析。句意为“我们对于写作的起始有了相当准确的观点,演讲的。起源仍然是个谜团”。根据句意.前后表转折.故选C。
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