It's necessary for us to have a meeting.为什么要在不定式前+to呢?请问?to在这句子中有何用意?谁给我正确答案?我可以用be necessary

it's necessary for you to give up smoking(保持句子原意) it's necessary ____you____smoke It‘s necessary for us___(learn)English well说明原因 英语翻译It's necessary for us to have a meeting. it's necessary for us to have healthy eating habits it's necessary for us to have healthy eating it's necessary for you___(eat)three meals a day It's necessary for sb.to do.(中文意思） it's necessary是什么意思 it necessary it necessary for是不是it's necessary for的简单形式,请问它原来的结构是什么?我记得这好像是个简单形式 应该是It's necessary for keep fit.为什么正确答案确是It's necessary to keep fit. 是it's necessary for us to sleep for 8 hours 还是is' necessary for us to sleep 8 hours? I thought____us students to have plenty of exercise every day.A.It's necessary to B.it necessary for C.it necessary of D.it's necessary of请教选什么为什么 it's necessary for us to learn english well同义句 it's necessary aand important for students to take enough exercise It's necessary for kids to ___ ___ ___(与.多交流) their parents 英语填空：It's necessary for us to p_____ speaking English every day. it's necessary for us to do someting_______(make)our city cleaner us study necessary to hard it’s for 连词成句