单选题 Millions of Americans take vitamins and minerals, ______ that these pills can help to prevent serious illnesses.

【正确答案】 A

【答案解析】[解析] 本题考查非谓语动词的用法。本句为非限定性定语从句的省略，原句为who are convinced that。be convinced that表示“确信，信服”，先行词是Americans，省略后应为convinced that，为过去分词作定语，故选A。