it is not necessary a bad thing.麻烦解释一下句子的结构 ,为什么是用necessary而

when it is necessary 为什么可以变为when necessary? It is demanded / necessary / a pity + that…结构中的主语从句的谓语动词要用sh It is not necessary to have a new building in our school.的同义 求find it necessary和lt is necessary的解释 it is necessary . It is necessary to do 的例句 Change is not necessary to life,it is life It is not necessary to be a scient to make a diffence. It is not necessary to be a great scientist to make a ddiffe it is not necessary to be a great scientistmake a difference it is necessary for me to take a taxi中用动词来代替it is necessary It is not necessary to understand things in order to argue a