【题目】When first _____ to the market, these products enjoyed great success.
A.introducing
B.introduced
C.introduce
D.being introduced

【答案】B
【解析】when引导的时间状语从句是一个省略句，补全为 “When they were first introduced to the market, …”。全句意思为：“这些产品一投放市场，就获得了成功。”