1, Ba likes bird-watching.

2, I have oily skin, so I wash my face regularly.

3, I haven't visited Lan for a week.

4, I think listening to music is useful.

$1. $ Ba's likes bird-watching

$→$ S + like(s) + Ving : Thích làm gì

$2. $ I have oil skin so I wash my face regularly

$→$ So là liên từ chỉ kết quả

$3. $ I haven't visited Lan for a week

$→$ S + last + Ved + time + ago : Lần cuối cùng làm gì

$→$ S + have/ has + not + for + time

$4. $ I think (that) listening to music is useful

$→$ S + find + N / V-ing + adj

$→$ S + think + N / V-ing + is + adj

`@Chamian`