let's反意疑问句let's改反意疑问句究竟用shall we还是shan't we?两者有什么区别呢?为什么很多例句都写两个都可以?

Let's开头的祈使句,在反意疑问句中,反意疑问部分为什么? Let 's go there 反意疑问句 Let's 与Let us的反意疑问句 Let's go down.改为反意疑问句为Let's go down（ ）（ Let’s make fruit salad.(完成反意疑问句) Let’s make fruit salad--------- ----------? Let’s cheer him up.(改为反意疑问句)Let’s cheer him up, 把Let's go to school改为反意疑问句 let‘s go to the zoo 改为反意疑问句 改成反意疑问句 Let's go to the park. let's make milk shake(改为反意疑问句) Let‘s go shopping.改为反意疑问句是什么? Let's go to school,___ ___?(反意疑问句) Let's go home,______ ______?（反意疑问句） 完成反意疑问句 Let's clean the room,__________? let's sell books____ _____ (改为反意疑问句) Let's get out of here,( )( 反意疑问句 let's do it by ourselves 完成反意疑问句 let us go,.../let me go,.../let's go,...三句话的反意疑问分别是什么呢?