参考答案：B

解析：[分析] 结构识别require是及物动词，常用require sth. /doing；require sb. to do sth. 例：The floor requires washing. 地板该洗了。I require two children to help me. 我需要两个孩子来帮我的忙。它还常用于：be required to do something，例：All passengers are required to show their tickets.所有乘客都必须出示车票。