1.There is=>are children in front of the trees.
2.I am=>We are your best friends.
3.There is=>are pens under the book.
4.He has got an orange=>oranges in his hands.
5.She has got a child=>children.
6.My neighbor=>neighbors usually buy in this shopping center.
7.I don't like this=>these books.
8.These are the best cake=>cakes I've ever eaten.