1.Mary had been seriously ill since last night ( HTHT )
2.They sometimes go school by bus ( HTĐ ) chủ ngữ số nhiều động từ giữ nguyên
3.How long have you studied English ? ( HTHT)
- l studied it for 7 years.
4.We last saw them last Sunday.( QKĐ )
5.l haven't met him since he moved to Hanoi.( HTHT)
6.Now they are playing happily in the school yard( có dấu hiệu là now => HTTD )
