we are going to have a welcome party这里为什么要加a ,不加不行吗还有 we plan to visit our cities这里的city为什么要变成复数呢?请老师给讲解下

Where are we going to have it? We are going to have a picnic on next Sunday. 改错:We are going to have an football match. we are going to have a class t______? holiday,we,going,are,have,to,a连词成句 We are going to have a sports day next Monday. We are going to have a 还有,下面的扩句填什么好?We are going to have a Picnic．We are going to have a Picnic＿We are going to have a Picnic＿＿ have,to,we,a,good,are,going,time.(排序) We are going to have a picnic ( ) tomorrow morning We are going to have a barbecue _______ it r.. We are going to have the weather tomorrow~求翻译! going,are,have,lunch,we,to,together.连词成句 We are going to have a sports day next are we going to have Science by the we are going to have a party tonigh.engoy_____. We are going to have a holiday the month ( ) next we are going to have a holiday if it( )October we are （）going to have any classes next week