单选题 The captain was ______ to sergeant for failing to fulfill his duties.
A. regulated B. promoted C. deregulated D. demoted

【正确答案】 D

【答案解析】demote意为“使降级，使降职”，如：be demoted from captain to lieutenant；统领降为副手；regulate管制，控制；promote促进，发扬，提升；deregulate解除管制。