I. Fill in the blanks with the correct tense of the verb .Each sentence uses one pair of verbs
Ask/ come                  Catch/leave                break/get
go/invite.        ring/be           make/buy.       be/hurry.  
learn/be.        have/buy          understand/help
1.I     no money left if I      that expensive book
2.Alex        late if he (not)          up!
3.If you (not)           I        you with the exercise
4.Greg        the train if he.          soon
5.(you)          to the party if they          you?
6.The bell.          if there      a fi're
7.The bike       if all three of you.      on it 
8.If you(not)         how to use a computer it.      hard to find a job
9.(your sister)           a pullover for me if I       the wool
10.If I        him nicely i think he.      to the mmovies with me