The correct answer is option 3, Vitamin C. Deficiency of Vitamin C can lead to bleeding of gums and loosening of teeth. Vitamin C is essential for maintaining the health of gum tissue and preventing gum diseases such as gum bleeding and periodontitis. It is also necessary for the production of collagen, a protein that helps in the formation and maintenance of healthy teeth and gums. Lack of Vitamin C weakens the gum tissue, leading to gum bleeding and tooth loosening. Vitamin A is important for maintaining healthy skin and eyes, but it is not directly linked to gum health. Vitamin B and Vitamin D are also crucial for overall health, but they do not specifically affect the gums and teeth.