Option 1: Vitamin D is not considered very labile and is not easily destroyed during cooking or storage. It is more resistant to heat and is not as sensitive to light and air.

Option 2: Correct Answer. Vitamin C is indeed very labile and easily destroyed during cooking as well as storage. It is sensitive to heat and is easily oxidized when exposed to air, making it prone to degradation.

Option 3: Vitamin B6 is relatively stable and is not easily destroyed during cooking or storage. It can withstand moderate heat and is not significantly affected by light or air.

Option 4: Vitamin K is also relatively stable and is not easily destroyed during cooking or storage. It is not sensitive to heat and is generally resistant to light and air.

Therefore, the correct answer is Option 2, vitamin C. It is important to handle foods rich in vitamin C carefully to retain its nutritional value.