When first to the market, these products enjoyed great success.
A. being introduced
B. having introduced
C. introduced
D. introducing
网友回答
A. being introduced
B. having introduced
(答案→)C. introduced
D. introducing
解析：这是When引导的省略句，应为：When they were first introduced to the market，这里省略了they were，故选C。状语从句的省略，注意状语从句中的主语同主句主语的一致性，并且从句的主语后有be 时，这时主语和be一起省略。