1.Hoa's aunt and uncle used to (stay)....stay.. in Hue                            
2.My dad (work)..works.. for his company for 20 years
3.Minh (do)...did.... his Math homework yesterday
4.Ba is not old enough (carry)..to carry... these boxes
5.we ought to(study)...study...harder
6.lan is going to(watch).....watching...an action movie tonight
7.my sister(visit)...visited ...da lat last week
8.do you mind(help)..helping...me with these exercises?
9.do you mind if i(close)..close.the window?
10.would you mind if i(turned)...on the music?
11.would you like me(lend)...you some books?
12.i wanted(go)...shopping yesterday
13.the local people are interested in(Conserve)...natural tesources