it is necessary .
it is necessary .
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?
求find it necessary和lt is necessary的解释
Is it necessary to learn grammer
英语语法问题 it is necessary that
It is necessary that he (take) _take__some
It is necessary for sb to
It is necessary to do 的例句
it is necessary that the plan__before june
it have been necessary 和 it is necessary 的区别?请问下句中it had bee
it is necessary for me to take a taxi中用动词来代替it is necessary