Here are the best answers for each of the sentences:

1. We **have gone** snorkeling to see beautiful coral reefs several times. (C)
2. Sarah **has put up** her tent for the camping trip yet. (A)
3. The camping trip was very memorable. I **had** such exhilarating experiences before. (D)
4. They **have just come** back from their vacation in Da Nang. (D)
5. Nam **has been** an eco-tour since he was 12 years old. (A)
6. Last night, I **learnt** by heart to prepare for the final test. (B)
7. **Have** you ever had an embarrassing experience while giving a performance in front of the crowd? (A)
8. We **did not take** any photos of the local wildlife since we got here. (B)

These answers should fit well in the context of the sentences.