`1`. We used to to in London when I was a child.
`->` used to + Vinf: đã từng làm việc gì trong quá khứ
`2`. She wishes she could play the piano.
`->` Câu mong ước nên lùi thì từ "can" thành "could"
`3`. If I didn't speak Englis badly, I could speak to Linda.
`->` If 2: If + S1 + V2/ed, S2 + would/could + Vinf
`4`. I began to study/ studying Englis 2 years ago.
`->` S + began + to V/ Ving + thời gian + ago