Here are the correct answers for the given sentences:

1. **Tan Son Nhat Airport is heavily __ during public holidays.**
- **b. congested**
- **Correct sentence:** "Tan Son Nhat Airport is heavily congested during public holidays."

2. **Food waste can be collected and __ into biogas with no harm to the environment.**
- **d. processed**
- **Correct sentence:** "Food waste can be collected and processed into biogas with no harm to the environment."

3. **We are looking for someone who is __ and hard-working.**
- **c. reliable**
- **Correct sentence:** "We are looking for someone who is reliable and hard-working."

If you need any further clarification or help, feel free to ask!

Here are the correct answers for each question:

1. Tan Son Nhat Airport is heavily **b. congested** during public holidays.
2. Food waste can be collected and **d. processed** into biogas with no harm to the environment.
3. We are looking for someone who is **c. reliable** and hard-working.

1. Tan Son Nhat airport is heavily **b. congested** during public holidays.

2. Food waste can be collected and **d. processed** into biogas with no harm to the environment.

3. We are looking for someone who is **c. reliable** and hard-working.