2 visited - had been
vế visted ta chia thì QKĐ : S + v-ed / v2
dấu hiệu nhận bt : yesterday
vế had been ta chia thì QKHT : s + had + VPII
3 travels
thì HTĐ , diễn tả sự thật : S + vs/es
4 were having - went
when+ thì QKTD , thì QKĐ
S + was / were + V-ing