It is necessary ( ) others when they are in trouble.Do you think so?A.for us to help B.of us helping C.of us to help D.for us helping

if it is necessary /if necessary /when it is necessary 意思一样吗 when it is necessary 为什么可以变为when necessary? it is necessary for you to work Is it necessary to learn grammer It is necessary for sb to early 是什么副词It is certainly necessary! It is necessary to do 的例句 i feel it necessary 的句子成分分析下为啥不是 it is necessary 关于necessary.it is necessary to do sth.it is nec关于necessary. it is necessary to do sth. it is necessary to doing sth. 两者有什么区别?什么时候用to do .什么时候用 to doing?请回答, we think that is necessary还是we think that it is necessary is it necessary to tell his father everything?此句用is that necessary Change is not necessary to life,it is life it is clear that sleeping is necessary to everyone 英语necessary的问题It is necessary for us to learn.可不可以改成We are necessary to learn The indoor swimming pool seems to be a great deal more luxurious than ( )A is necessary ;B being necessary ;C to be necessary ;D it is necessary Never give him more money than___?A.being necessary B.is necessary C.it is necessary D.what necessD.what necessary We consider _________the instrument be adjusted each time it is used.选项:a、that it necessaryb、it necessary thatc、 necessary thatd、necessary of it that It is necessary to protect trees from the frost.翻译