The correct answer is option 1, Vitamin-C. An antioxidant is a substance that helps protect the body from the damage caused by harmful molecules called free radicals. Free radicals are produced in the body during normal metabolic processes and can also be generated by exposure to environmental factors such as radiation and pollution. They can cause oxidative stress, which has been linked to various chronic diseases.

Vitamin-C, also known as ascorbic acid, is a powerful antioxidant that helps neutralize free radicals and protect cells from damage. It is found in many fruits and vegetables, such as oranges, strawberries, broccoli, and bell peppers. Vitamin-C also plays a crucial role in collagen synthesis, immune function, and wound healing.

Vitamin-K (option 2) is not an antioxidant but is important for blood clotting and bone health. Vitamin-B (option 3) refers to a group of vitamins that have various functions in the body, but they are not primarily known for their antioxidant properties. Vitamin-D (option 4) is necessary for calcium absorption and bone health but is not an antioxidant.