Grapes are generally dried in:

✅Explanation: Grapes are traditionally and most commonly dried in the sun to produce raisins. Sun-drying is a natural and cost-effective method that has been used for centuries. The grapes are spread out on trays or racks and exposed to sunlight, which evaporates the moisture and concentrates the sugars, resulting in the characteristic sweet and chewy texture of raisins.

• Why Sun Drying is Preferred:
Traditional Method: Sun drying is the most traditional and widely used method for producing raisins, especially in regions with abundant sunshine.
Cost-effective: It does not require any specialized equipment or energy input, making it a cost-effective option for farmers.
Unique Flavor: Sun-dried raisins are known for their distinct flavor profile, which is developed through the natural drying process under the sun.

📌Other Options Explanations:
(b) Dehydrator: Dehydrators are used for drying grapes, especially in regions with less sunlight or for faster drying. However, they require energy input and may not produce the same flavor profile as sun-dried raisins.
(c) Vacuum Drier: Vacuum driers are used for drying delicate products.
(d) Spray Drier: Spray drying is a method used for drying liquids into powders.

🛑 Additional Information:::
When raisins are placed in water, the water from the surrounding diffuses into the raisins and so the raisins swell up.
​This process is called osmosis.
When dried raisins are placed in a concentrated salt solution, they will shrink. 
A raisin, when put in a salt solution (or any other concentrated solution), loses water by exosmosis and consequently shrinks.
This happens due to osmosis.
It is the passage of water from a region of high water concentration to a region of lower water concentration