1/ sleeping ( HTTD ; dấu hiệu : right now )
2/ bought ( QKĐ ; dấu hiệu : yesterday ) - going to ( be going to )
3/ is attending ( HTTD ; dấu hiệu : at the moment )
4/ hasn't had ( HTHT ; dấu hiệu : for )
5/ starts ( HTĐ )
6/ have studied ( HTHT ; dấu hiệu : since )
7/ came ( QKTD )
8/ have done ( HTHT )
9/ am ( HTĐ )
10/ has waited ( HTHT ; dấu hiệu : for )
11/ called ( QKTD )
12/ was ( QKĐ )
13/ am talking ( HTTD ; dấu hiệu : at the moment )
14/ were ( QKĐ ; dấu hiệu : last year )
15/ rises ( HTĐ )
16/ met ( QKĐ ; dấu hiệu : yesterday )
17/ takes place ( HTĐ ; dấu hiệu : every four years )ư
18/ were playing ( QKTD ; dấu hiệu : a 4pm yesterday )
19/ was cooking ( QKTD )
20/ are playing ( HTTD ; dấu hiệu : now )
21/ saw ( QKTD )