1. Although she was ill, she went to school yesterday.
2. The girl whose parents are engineers is Mary.
"Her parents" `=>` whose.
3. Unless you take the taxi, you will be late for the meeting.
Take the taxi or you will be late for the meeting.
If not = Unless.
4. I wish I had a bicycle.
Câu điều ước trái với hiện tại, câu gốc ở HTĐ, viết lại bằng QKĐ.