Here are the correct answers for each of the blanks in the passage:

1. **C. that**
- The correct sentence would read: "One traditional food in Vietnam that is loved by many is the pickled vegetables..."

2. **C. speciality**
- The sentence becomes: "The speciality of the pickled vegetables is also enhanced by the addition of spices such as garlic, chili, and coriander."

3. **A. Although**
- This would form: "Although the simplicity of the ingredients, the original recipe for pickled vegetables still has been..."

4. **A. handed**
- The entire phrase would read: "...the original recipe for pickled vegetables still has been handed down through generations..."

5. **A. preserve**
- This makes the final sentence: "It's a perfect example of how traditional food preserve methods can create delicious and healthy dishes."

Therefore, the completed passage with correct answers would be:

"One traditional food in Vietnam **that** is loved by many is the pickled vegetables, also known as 'dưa muối' in Vietnamese. This dish is made by preserving a variety of vegetables such as carrots, daikon radish, and cucumber in a brine solution made of salt, sugar, and water. The vegetables are left to ferment for several days, which gives them a tangy and savory flavor. The **speciality** of the pickled vegetables is also enhanced by the addition of spices such as garlic, chili, and coriander. This dish is often served as a side dish or used as a topping for other Vietnamese dishes such as bánh mì or bún chả. **Although** the simplicity of the ingredients, the original recipe for pickled vegetables still has been **handed** down through generations and remains a staple in Vietnamese cuisine. It's a perfect example of how traditional food **preserve** methods can create delicious and healthy dishes."