单选题 She ______ and lowered her head when she couldn"t answer the question in the presence of her classmates.
【正确答案】 B
【答案解析】[解析] 动词词义辨析。根据句中lowered her head, couldn"t answer the question说明她什么也干不了。选项中，defy通常的意思是“挑衅，不服从，公然反抗”，但还有“使落空”的意思，符合句意。故答案为B。