REDUCED RELATIVE CLAUSES: 1. The next train which leaves the station is to London. 2. The road which connects Hanoi and Ho Chi Minh city is called Number 1 3. The man who sat next to me on the train looked gentle. 4.. The steam engine which was invented by James Watt opened a new period in human development history. 5. I felt sorry for Paul, who was the only child on the block. 6. The car which is running quickly is red color 7. The boy has a ball which he kicks everyday.

27. The next train which leaves the station is to London.
=> The next train leaving the station is to London.
28. The road which connects Hanoi and Ho Chi Minh city is called Number 1
=>  The road connecting Hanoi and Ho Chi Minh city is called Number 1
29. The man who sat next to me on the train looked gentle.
=> The man sitting next to me on the train looked gentle.
30. The steam engine which was invented by James Watt opened a new period in human development history.
=> The steam engine which invented by James Watt opened a new period in human development history.
31. I felt sorry for Paul, who was the only child on the block.
=> I felt sorry for Paul, the only child on the block.
32. The car which is running quickly is red color
=> The car running quickly is red color
33. The boy has a ball which he kicks everyday.
=> The boy has a ball for him to kicks everyday.

Giải thích:
Rút gọn mệnh đề quan hệ:
   - T/h 1: Khi trước danh từ có các từ xác định như: first, second, third, last, next, only… hoặc trong câu có cấu trúc so sánh hơn nhất.
  + Rút gọn ĐTQH và động từ thành dạng to V nếu V được chia ở thể chủ động
  Eg: Yuri Gagarin was the first person who flew into space.→ Yuri Gagarin was the first person to fly into   space.
  + Rút gọn ĐTQH và động từ thành dạng to be P2  nếu V được chia ở thể bị động
 Eg: This is the second person who was killed in that way. → This is the second person to be killed in that way.
  - T/h 2: Khi trước danh từ không có các từ xác định như: first, second, third, last, next, only…
 + Rút gọn ĐTQH và động từ thành dạng Ving nếu V được chia ở thể chủ động
 Eg: The fence which surrounds our house is made of wood.→ The fence surrounding our house is made of wood.
 Chú ý: Nếu V là động từ “to be” thì bỏ luôn cả ĐTQH và động từ này chứ không rút gọn nó thành “being”
 Eg: The books (which are) on that shelf are mine.
 + Rút gọn ĐTQH và động từ thành dạng P2  nếu V được chia ở thể bị động
 Eg: They live in a house that was built in 2000. → They live in a house built in 2000.