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`1`.Plastic waste makes our ocean look unpleasant and more healthy.
→ Plastic waste makes our ocean look unpleasant and less healthy.
Lý do: "more healthy" sai về nghĩa, vì rác thải nhựa không làm đại dương trở nên "khỏe mạnh hơn" mà ngược lại. Phải dùng "less healthy" (kém khỏe mạnh hơn).

`2`.One of the most interesting and adventurous activity in Hạ Long Bay is kayaking.
→ One of the most interesting and adventurous activities in Hạ Long Bay is kayaking.
Lý do: "One of the" phải đi với danh từ số nhiều → "activity" → "activities".

`3`.Although most of us love collect seashells, overcollection of shells could harm the coastal ecosystems.
→ Although most of us love collecting seashells, overcollection of shells could harm the coastal ecosystems.
Lý do: "love" + V-ing → "collect" → "collecting".

`4`.Do they prefer healthy snacks than candy and ice cream?
→ Do they prefer healthy snacks to candy and ice cream?
Lý do: "Prefer" đi với "to" chứ không phải "than".

`5`.Healthy food impacts not only our physically health but also mental health.
→ Healthy food impacts not only our physical health but also mental health.
Lý do: "physically" là trạng từ, cần dùng tính từ "physical" để bổ nghĩa cho "health".

`6`.Many teens don’t consume enough important nutrients essential for her health.
→ Many teens don’t consume enough important nutrients essential for their health.
Lý do: "Many teens" (số nhiều) nên phải dùng "their" thay vì "her".

`7`.Eating a balanced diet and being active are two of the most important things we should do to stay healthful.
→ Eating a balanced diet and being active are two of the most important things we should do to stay healthy.
Lý do: "Healthful" thường được dùng để mô tả đồ ăn, còn "healthy" dùng để mô tả con người, lối sống.

`8`.Many teens don’t have enough sleep because of stay up late for homework.
→ Many teens don’t have enough sleep because of staying up late for homework.
Lý do: "Because of" + danh từ / V-ing → "stay" → "staying".