Rearrange the following sentences to form a coherent paragraph:
1. The key aim of this process is to make items safer to consume by reducing germs and impurities.
2. Food preservation refers to techniques used to keep perishable items from spoiling quickly.
3. These techniques may include drying, freezing, canning, and methods like salting or pickling.
4. Moreover, it helps retain quality, improves storage duration, and reduces overall food waste.

The correct option is 2, 3, 1, 4.

Let's break down the logical flow of the sentences to form a coherent paragraph:

1. Sentence 2 ("Food preservation refers to techniques used to keep perishable items from spoiling quickly.") introduces the main topic of the paragraph: Food preservation and its basic definition. Therefore, it serves as the ideal introductory sentence.

2. Sentence 3 ("These techniques may include drying, freezing, canning, and methods like salting or pickling.") directly follows sentence 2 by using the demonstrative phrase "These techniques" to elaborate on the specific methods used in food preservation.

3. Sentence 1 ("The key aim of this process is to make items safer to consume by reducing germs and impurities.") expands on why "this process" (food preservation) is carried out, highlighting safety and germ reduction.

4. Sentence 4 ("Moreover, it helps retain quality, improves storage duration, and reduces overall food waste.") uses the transition word "Moreover" to add additional benefits (quality retention, extended storage, waste reduction) to the primary aim mentioned in sentence 1.

Thus, the logical and coherent order of sentences is 2, 3, 1, 4.