The correct answer is option 3: Pancreas. The pancreas is the largest mixed gland of the human body. This gland serves as both an endocrine gland and an exocrine gland. As an endocrine gland, it produces and releases hormones directly into the bloodstream, such as insulin and glucagon, which regulate blood sugar levels. As an exocrine gland, it secretes digestive enzymes into the small intestine to aid in the digestion of carbohydrates, proteins, and fats. The thymus is indeed a gland in the body, but it is not the largest mixed gland. The liver is the largest gland in the body, but it is not considered a mixed gland as it does not have both endocrine and exocrine functions. The spleen is also a gland, but it is not the largest mixed gland.