1.Gary had played tennis when his friends a. comes
b. come
c. came
d. coming
2.Before he fell in love with Susan, he steady with Belen. 
a. has gone
b. have gone
c. had been going
d. had gone
3.She had thrown the box when her mother for it
a. asked
b. ask
c. asks
d. asking
4.After Leonardo da Vinci _______ the flight of birds, he designed the ornithopter, a flying machine.
a. had studied
b. has studied
c. has been studying
d. have studied ​