a. They sell jeans all over the world. → ...................................................................................................... b. They sold their house last week. → ...................................................................................................... c. They have found oil in the Antartic.. → ...................................................................................................... d. They will build a new school in our village. → .................................................................................................... e. They did this exercise in 30 minutes. → ...................................................................................................... f. We can do this exercise in 30 minutes. → ...................................................................................................... g. You must do this exercise carefully. → ...................................................................................................... h. We have to do this exercise carefully. → ...................................................................................................... i. They grow rice in tropical countries. → ...................................................................................................... j. People should stop experiments on animals. → ...................................................................................................... k. Someone gave Mary this present yesterday. → ...................................................................................................... l. You should invite Lan to the party. → ........................................................