when it is necessary 为什么可以变为when necessary?

when it is necessary 为什么可以变为when necessary? if it is necessary /if necessary /when it is necessary 意思一样吗 It is necessary ( ) travellers to take a map when It is necessary for to do first aid when we _____ someone injured in an accidentJia 英语作文:It is necessary for freshmen to have a laptop when they go to university? 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 if you don't want to get into trouble .say no without hesition when it is necessary i feel it necessary 的句子成分分析下为啥不是 it is necessary When your design is done,it is usually necessary to present the results to your client peers,or em机械英语翻译不要有道翻译的 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