(sth．is)required ot’sb．／require sth．of sb．为固定搭配，意思是“要求某人……”，如：Silence is required of all the examination candidates(所有应试者都需保持安静。)B符合题意。
【点睛】词汇线索题。lack意为“缺乏”，可作及物动词，直接接宾语：作不及物动词时常用于sb．be lacking in sth．或sth．be lacking结构，如：He is lacking in courage．(他缺乏勇气。)face意为“(使)丽对”，为及物动词，如：The difficulty that faces US is the number of those in need．(我们面临的困难是需要帮助的人太多。)另外也可用于be faced with结构。confront意思与face相近，意为“(使)碰到，(使)遇到”，为及物动
词，常用于be confronted with结构，如：We are now confronted with many difficulties．(我们现在面临很多困难。)