I. 

3. I think ice skating is interesting. ( Find ... + Adj = Think ... is adj )

II.

1. They have visited Ha Long Bay many times. ( Dấu hiệu : Many times )

2. My brother doesn't like ice-skating because he thinks it is dangerous ( Thì hiện tại đơn )

3. Did they visit their grandparents last Sunday ? ( Dấu hiệu : Last Sunday )

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@Nhi

3. I think ice - skating is interesting

Cấu trúc: 

(+) I think (that) + Clause

(-) I don't think + Clause

II.

1. They have visited Ha Long Bay many times. (many times là dấu hiệu nhận biết thì hiện tại tiếp diễn)

Cấu trúc: (+) S + have/has + Ved/VpII

2. My brother doesn’t like ice-skating because he thinks it is dangerous.

Dịch: Anh trai tôi không thích trượt băng vì nghĩ rằng nó nguy hiểm. 

3. They visited their grandparents last Sunday? ( last Sunday là dấu hiệu nhận biết thì quá khứ đơn )