The correct option is (b) Salmonella.
Explanation:
Salmonella typhi causes typhoid fever in human beings. It is characterised by constant fever due to the infection of intestine. Giardia is a flagellate protozoan, lamblia species of this protozoan causes disease giardiasis, a prolonged diarrhoeal disease of humans.
Bacterial genus Shigella causes shigellosis or bacillary dysentery,
Escherichia coli is a facultative anaerobes, found in the intestine of human beings.