问题补充：
When first to the market, these products enjoyed great success.
A. introducing
B. introduced
C. introduce
D. being introduced
答案：
A. introducing
(答案→)B. introduced
C. introduce
D. being introduced
解析：考查非谓语动词作状语的用法。introduce 与主语these products为动宾关系所以用过去分词做状语。“首次引入市场这些产品就获得了巨大成功”选B
