句子开头是there is怎么改为复数形式?

句子开头是there is怎么改为复数形式?
句子开头是there is怎么将其改为复数形式?下面有一些题目,麻烦厉害的朋友帮我的忙
例:There is a pencie on the desk
There are some pencies on the desk
1.There is a watch on the table.
2.There is a knife near that tin.
3.There is a policiman in the kitchen.
4.There is a cup on the table.
5.There is a letter on shelf.
6.There is a peach on the desk.
7.There is a passport on the shelf.
8.There is a fish in the cupboard.
9.There is a tree in the garden.
10.There is a boat on the river
如果回答者能告诉我为什么要这样改那就更好了,简短一点就好!