She will help you when it necessary怎样改

She will help you when it necessary怎样改 she will help you if necessary 同一句 The guide（ will help） you when it（ is） necessary.请问这个写的对吗(⊙_ --------(if,but,because)necessary ,i will come to help you. It is necessary for you to help each other. When you___,people around you will help you to correct it The police will help you when n_____. You can ask ____（任何人）in this team for help when necessary when it is necessary 为什么可以变为when necessary? 填介词 I will help you ( ) it There is no do__ that we will help you if necessary. It will help you if you will let