单选题 China moved to ______ its grain production when its grain output had kept declining for five consecutive years.
A. turn up B. take up C. step up D. make up

【正确答案】 C
【答案解析】turn up：出现，露面；take up：占用，着手于，开始做……，拿起；step up：增加；make up：编造，构成，弥补(for)