1. Smartphones can store audio books. They have a lot of storage space.
Câu viết lại:
Smartphones which have a lot of storage space can store audio books.

 Giải thích (Việt):
Ta nối 2 câu lại bằng mệnh đề quan hệ "which" để bổ nghĩa cho "smartphones".
– “They” chính là “smartphones”, nên thay bằng which.

 Explanation (English):
We use "which" to replace "they", referring to "smartphones", to form a relative clause that adds information about the smartphones.

2. They talked to a boy. His bicycle broke down in front of the shop.
 Câu viết lại:
They talked to a boy whose bicycle broke down in front of the shop.

 Giải thích (Việt):
Sử dụng "whose" để chỉ sự sở hữu (xe đạp của cậu bé).
– "His bicycle" → "whose bicycle"

 Explanation (English):
We use "whose" to show possession – "his bicycle" becomes "whose bicycle".

3. My sister teaches me how to use a laptop. She is good at computers.
 Câu viết lại:
My sister, who is good at computers, teaches me how to use a laptop.

 Giải thích (Việt):
Mệnh đề "who is good at computers" bổ nghĩa cho “my sister”, dùng "who" vì là người.
Đây là mệnh đề không xác định (có dấu phẩy) vì chủ ngữ đã xác định rõ.

 Explanation (English):
We use "who" to refer to "my sister" (a person). This is a non-defining clause (set off by commas) because "my sister" is already specific.

4. The girl has designed this invention. She is only 11 years old.

 Câu viết lại:
The girl who has designed this invention is only 11 years old.

 Giải thích (Việt):
Ta dùng "who" để nối mệnh đề bổ nghĩa cho "the girl".
"She" → "who"

 Explanation (English):
We use "who" to replace "she", referring back to "the girl", and form a defining relative clause.

5. He was sitting on a chair. It was uncomfortable.
 Câu viết lại:
He was sitting on a chair which was uncomfortable.

 Giải thích (Việt):
Ta dùng "which" để thay thế cho "it" (chỉ cái ghế) → mệnh đề quan hệ bổ nghĩa cho "a chair".

 Explanation (English):
We use "which" to replace "it", referring to "a chair", and add more information using a relative clause.