Answer: c) capsule
Explanation: The capsule is the most external layer of the bacterial envelope and is composed of complex carbohydrates. As it prevents the bacterium from drying out as well as phagocytosis from macrophages, it enhances this microorganism's ability to cause disease. Thus, it is considered a virulence factor and is present in all the major disease-causing bacteria. Those individuals that are lacking it due to mutations, do not cause any disease.
