i'm going to the supermarket with my mother为什么要加with

和我的妈妈当然要加with了with的用法介词with的复合结构,常见形式及用法：1、with+现在分词They started working with the machine running。2、with+过去分词 He is used to sleeping with the window closed。3、with+不定式（to do）With a lot of homework to do,Tom cann't go out to play。4、with+形容词She left the house with the windows open(开着的）/closed。（关着的）。这里的形容词有普通形容词,也有像closed,broken等过去分词演变的形容词。但只要明白语义,理解起来并不难。5、with+副词Don't leave the room with the lights on。6、with+名词（包括名词性短语）/代词The boy killed two birds with a stone his weapon。7、with+介词短语The teacher came into the classroom with a book in his hand在句尾的“和”要用“with”