18.Option C is correct. Clostridium tetani is a spore-forming Gram-positive rod-shaped bacterium. It is an obligate anaerobe and the major route of transmission is through wounds contaminated with soil or foreign bodies. 19.Option A is correct. Tetanospasmin is the most potent toxin produced by Clostridium tetani, the causative agent of tetanus. It acts on the nervous system and causes muscle contractions and spasms. 20.Option B is correct. Clostridium botulinum is a spore-forming bacterium that causes botulism. Its growth is stimulated by neutral or alkaline pH food types. It causes foodborne illness due to ingestion of preformed toxin in contaminated food, known as foodborne intoxication. It is not a major cause of wound or infant botulism.