The vitamin which is liable to be destroyed during cooking is Vitamin C.

Explanation:
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin that is easily destroyed by heat, light, and air. Cooking causes the breakdown and loss of this vitamin, resulting in reduced nutritional value in the cooked food.

Heat Sensitivity of Vitamin C:
- High temperatures: Vitamin C is highly sensitive to high temperatures. When exposed to high heat during cooking, such as boiling or frying, the vitamin C content in foods can significantly decrease.
- Prolonged cooking: The longer the cooking time, the more vitamin C is destroyed. Extended cooking can lead to a substantial loss of this vitamin.

Methods of Cooking that Destroy Vitamin C:
- Boiling: Boiling foods containing vitamin C can cause the vitamin to leach out into the cooking water, resulting in a significant loss of the nutrient.
- Steaming: Steaming is a gentler cooking method that helps retain more of the vitamin C content compared to boiling. However, some loss of vitamin C can still occur.
- Microwaving: Microwaving is a quick method of cooking that helps to preserve more of the vitamin C content compared to other cooking methods. The shorter cooking time and minimal exposure to heat help retain more nutrients.

Benefits of Vitamin C:
- Antioxidant activity: Vitamin C is a powerful antioxidant that helps protect cells from damage caused by free radicals.
- Immune system support: Vitamin C plays a vital role in supporting the immune system, helping to fight off infections and promote overall health.
- Collagen synthesis: Vitamin C is necessary for the production of collagen, a protein that contributes to the health of the skin, bones, and connective tissues.
- Iron absorption: Vitamin C enhances the absorption of non-heme iron from plant-based sources, improving iron levels in the body.

Conclusion:
In conclusion, Vitamin C is the vitamin most susceptible to destruction during cooking. It is highly sensitive to heat and can be easily lost through boiling, prolonged cooking, and exposure to high temperatures. To retain the maximum amount of vitamin C in foods, it is best to opt for cooking methods that involve minimal heat and cooking time, such as steaming or microwaving.