The monkey is siting in the tree.
Miss Smith is looking at a picture.
Mrs.Richards is taking off her coat.
Tim is sharpening his pencil.
He is swimming in the pool.
The children are going out of the building.
Two girls are walking along the river.
Is Mary doing her homework?
Simon and I are having our lunch.
改错中要注意的就是动词的用法,还有动词和介词的搭配考得很多.