Here are a book and two pens.对的话什么时候用到啊?知道的人快说啊,

Here are a book and two pens.对的话什么时候用到啊?知道的人快说啊, There( are )(a book)and (two pens)(on) the desk There are a book and two pens on the desk . 连词成句：there,a,book,and,pens,two,are,desk,the,on(.) There is (a book and two pens) in the bag.（对括号部分提问） there were a book and two pens on the desk There a book and two pens on the desk. There is a book and two pens on the desk. There are a pencil and two pens on the desk. On the desk____a book and two pens.横线里填is 还是are? There__a book and two pens on the desk just now.A.was B.were There __ a book and two pens on the desk.答案是is.为什么