=>

20. My father goes to work by motorbike.

-> by + phương tiện (bằng gì)

21. You should do morning exercises every morning.

-> should V: nên làm gì

22. You must arrive on time at school.

-> must V: phải làm gì

23. That car is more expensive than this one.

-> so sánh hơn tính từ dài more adj than

24. The air in the city is often more polluted than the air in the countryside.

-> so sánh hơn more adj than

25. How often do you go to the English Club?

-> how often (hỏi mức độ thường xuyên)

26. My brother usually walks to school.

-> go to school on foot ~ walk to school