Choose the most appropriate alternative word
Influenza : Virus :: Typhoid : ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Bacteria
The pair links a disease to the kind of germ that causes it: influenza is caused by a virus. Typhoid is caused by the bacterium Salmonella Typhi, so the matching word is bacteria.
Why the other options are incorrect
Option (1) Parasite — Incorrect. A parasite is any organism that lives on or in another and feeds on it, such as tapeworms or lice; it names a way of life, not a kind of germ.
Option (2) Protozoa — Incorrect. Protozoa are single-celled animals such as Plasmodium (malaria) and Entamoeba (amoebic dysentery).
Option (4) Bacillus — Incorrect. Bacillus names the rod shape of some bacteria (and one genus); it is a shape within the group, while virus names the whole group.