1. The English exam was more difficult than I thought.

- easy (adj): dễ >< difficult (adj): khó

- So sánh hơn: Với tính từ dài: S1 + tobe + more + adj + than + S2

2. Although Ivy studied a lot of for her biology test, she didn't pass it.

- Clause 1. However, Clause 2: tuy nhiên

-> Although + Clause 1, Clause 2: mặc dù

3. You have to/ must remove your shoes and belts when you go through the airport security checkpoint.

- It's the rules + to V

-> S + have to/ must + V(bare): Ai đó phải làm gì

4. Laura doesn't need to take part in the sports day if she doesn't want to.

- It's not necessary + for sb + to V

-> S + don't/doesn't + need to + V(bare): Ai đó không cần phải làm gì