be necessary for sb./sth的反义词说是什么?

be necessary for sb./sth的反义词说是什么? be necessary for和 be necessary to的区别老师说be important to后面加人,如果还有下文用be important for sb doing sth那be necessary to 和be necessary是不是也是这种用法?还是说be necessary to do sth be necessary for doing st It is necessary for sb to be adj to sb 与be adj for sb 区别Smoking is harmful to one's healthIt is necessary for you to get there on time. be necessary for和be necessary to 有何区别 be sth for sb be vailable for sb. be true for sb. be down for sb It's necessary for sb.to do.(中文意思） be useful to sb还是for sb? be embarrassing to sb还是for sb? be important to sb还是for sb be rude to sb还是for sb be left for sb to be valuable for sb对吗 be necessary 关于it 做形式主语句子的几个问题（1）为什么有的时候是It be necessary for sb to do sth.有时候却用It be necessary of sb to do sth.差别在哪里?比如：It is very difficult for me to do it.和It was very kind of him to pa