$\text{1.}$ She hasn't come back to her hometown for 4 years.
$\text{→}$ The last time + QKD + was = HTHT<phủ định> + for/ since
$\text{2.}$ He has worked as a bank clerk for 3 months.
$\text{→}$ S + started/ began + V-ing = HTHT<bỏ started/ began> + for/ since
$\text{3.}$ We haven't been to Singapore until 5 years ago.
$\text{→}$ Chúng tôi chưa từng đến Singapore cho đến 5 năm trước.
$\text{4.}$ I haven't had my hair cut since November.
$\text{→}$ S + last + QKD = HTHT<phủ định> + for/ since
$\text{5.}$ We haven't called each other for 5 months.
$\text{→}$ như câu 1
$\text{6.}$ We haven't met for a long time.
$\text{→}$ It is + time + since + S + last + QKD = HTHT<phủ định> + for/ since
$\text{7.}$ How long have you had it?
$\text{→}$ When did + S + V? = How long + have/ has + S + V<htht>?
$\text{8.}$ I have never had such a delicious before.
$\text{→}$ This is the first time + QKD + such (a/ an) + N = S + have/ has + never + V<htht> + such (a/ an) + before.
$\text{9.}$ The last time I saw him was 8 days ago.
$\text{→}$ như câu 1
$\text{10.}$ It is 4 days since I last took a bath.
$\text{→}$ như câu 6
