50, The teacher asked Tom what his mother was doing then
51, Many houses have been destroyed by the fire
52, I wish I had time to go around the city
53, I have worked for the company for 1 year
54, He has worked for this company for two years
55, If he prepared his homework, his teacher wouldn't get angry with hime
56, My father asked me if I was using his pen then
57, Nam swims very well
58, I used to wear Jeans
59, She used to be late for class
60, My father used to go swimming in the summer
61, She wishes she had enough time to revise all her lessons
62, They asked him what he did to do his mother
63, I will be given a computer by my parents on my next birhtday
64, I have studied in this school for four years
65, I haven't spoken to her for three years
66, The time machine will be showed to the public when they finish it
67, If you don't work hard, you won't pass your test
68, We wish we had had a new house
69, All the windows have to be cleaned by the students after class everyday
70, He told her nor to use that car
71, If you read the instructions carefully, you can install the smart phone

50: The teacher asked Tom what his mother was doing then
51: Many houses have been destroyed by the fire
52: I wish I had time to go around the city
53: I've worked for the company for a year
54: He has worked for this company for 2 years
55: If he doesn't prepare his homework, his teacher will get angry wiht him
56: My father asked me if I were using his pend then
57: Nam swims very well
58: I used to wear jeans
59: She used to be late for class
60: My father used to go swimming in the summer
61: She wishes she had enought time to revise all her lessons
62: They asked him what he did to help his mother
63: I will be given a new computer by my parents on my next birthday
64: I have studied in this school for 4 years
65: I haven't spoken to her for 3 years
66: The time machine will be shown to the public when they finished it
67: If you don't work hard, you won't pass your test
68: We wish we had a new house 
69: All the windows have to be closed by the students after class every day
70: He told her not to use that car
71: If you don't read the instructions carefully, you can't install the smart phone