Glands are specialized organs that produce and secrete substances, such as hormones, enzymes, or other fluids, for various bodily functions. The human body contains numerous glands, each playing a vital role in maintaining health.
Option B: Liver is the correct answer. The liver is not only the largest internal organ but also the largest gland in the human body, weighing about 1.5 kg (3.3 lbs) in adults. It performs over 500 vital functions, including detoxification, protein synthesis, and the production of bile, which aids in digestion. Option A, Thyroid, is an endocrine gland crucial for metabolism but is significantly smaller than the liver. Option C, Pancreas, is another vital gland involved in digestion and blood sugar regulation, but it is also much smaller than the liver. Option D, 'None,' is incorrect as the liver holds this distinction.