The correct answer is option 3: Proteins. Antibodies are a type of protein that play a crucial role in the immune system. They are produced by white blood cells called B cells in response to the presence of foreign substances in the body, such as bacteria or viruses.

Although options 1, 2, and 4 are all types of biomolecules, they are not specifically related to antibodies. Carbohydrates are organic compounds that primarily serve as a source of energy, while glycolipids are molecules composed of carbohydrates and lipids. Sterols, on the other hand, are a type of lipid that play a role in cell membrane structure.

It is important to note that while all antibodies are proteins, not all proteins are antibodies. Proteins are large, complex molecules made up of chains of amino acids. They have a wide range of functions in the body, from acting as enzymes to providing structural support. Antibodies, in particular, are a type of protein known as immunoglobulins and are specifically involved in immune responses.