1 ,is studying

2 ,is not going 

3 ,are studying

4 ,is having

5 ,is doing

6 ,is not going

7 ,is reading

8 ,are not working

9 ,is not being

10 ,are not playing

11 ,are not learning

12 ,are swimming

13 ,are not doing

14 ,doing-watching

15 ,is writing

16 ,are talking

17 ,is going-is going

18 ,are doing

19 ,are swimming

20 ,is not singing

21 ,is riding

22 ,are waiting

23 ,am playing-is watching

24 ,is driving

25 ,are sitting

26 , are doing-are watching

27 ,is studying

28 ,am not eating

29 ,is not listening

30 ,is having

Sử dụng thì HTTD

(+) S+am/is/are+V-ing

(-) S+am/is/are+V-ing

(?) am/is/are+S+V-ing