There are a pencil and two pens on the desk.

There are a pencil and two pens on the desk. There( are )(a book)and (two pens)(on) the desk There are a book and two pens on the desk . there ____ a pencil,two pens and there books on the desk,but There are some water and two pens on the desk. 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 ________ a ruler and two pens on the desk. 连词成句：there,a,book,and,pens,two,are,desk,the,on(.) There are two pens on the desk.(two pens就划线部分提问） There __ a book and two pens on the desk.答案是is.为什么