1. He hasn't written home for two months.
→ HTHT : S + have / has + not + `V_3` / `V_{ed}` + O
→ wrote → written
2. I haven't seen her for three years.
→ HTHT : S + have / has + not + `V_3` / `V_{ed}` + O
→ saw → seen
3. He has waited her since 2 o'clock.
→ HTHT : S + have / has + `V_3` / `V_{ed}` + O
→ wait → waited
4. Trung was not be at school last Tuesday.
→ QKĐ( tobe ) : S + was / were + not + V_nguyên mẫu + O
5. It is so expensive that my father can't buy for me.
→ Nó đắt đến nỗi bố tôi không thể mua cho tôi.