Question

【题目】Silk ______ one of the primary goods traded along the Silk Road by about 100 BC.
A.had become
B.was becoming
C.has become
D.is becoming

Answer 1

【答案】A
【解析】考查动词时态。句意：到公元前100年为止，丝绸已经成为丝绸之路上交易的主要商品之一。时间状语是by+过去时间，谓语用过去完成时。故选A。