1. It was an extremely frightened experience in my life.

-> frightening -> vật (tính từ đuôi ing)

2. Mark went on working despite he felt unwell.

-> although -> although + S + V = despite + N/Ving : mặc dù

3. My sister had worked in the bank for five years before she had been sent to Da Nang.

-> was 

4. Tom said that he had been very excited visiting Ha Long Bay for the first time in 2005.

-> to visit. Vì excited là tính từ ta sử dụng cấu trúc: It's + adj + to + V-infinitive

5. The country has significant changed since we came here in 2007. 

-> Significantly. Vì sau đt là trạng từ

`1`.Frightened→Frightening(Chủ ngữ là là vật→Thêm ing)

`2`.Despite→Although(Although+S+V(Clause):Mặc dù.......)

`3`.Had been→Was(Past perfect+Before+Simple past)

`4`.Visiting→To visit(S+Be+Adj+to-inf)

`5`.Significant→Significantly(Trạng từ+Động từ(changed)

$\text{@TriLeCongTri}$

$\text{chúc em học tốt!!!!}$