1. When he is 5, he used to go fishing with his father ⇒ When he was 5, he used to go fishing with his father.
2. It has about 5kms from my house to the city center. ⇒ It is about 5 kms from my house to the city center.
3. British people used to dringking tea all day. ⇒ British people used to drink tea all day.
4. He used to take a bus to work, but now he do. ⇒ He used to take a bus to work, but now he doesn't. ( có but giữa hai vế câu, vế đầu là câu khẳng định nên vế sau phải là câu phủ định hoặ câu ngược nghĩa với vế đầu )
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