Which is not a parasite?

Answer: (b) Housefly

Houseflies feed on waste and spread germs, but they don’t live on a host — not a parasite.

The idea

A parasite lives on or inside another living animal, takes its food from it and harms it. A housefly does not live on anyone. It feeds on rubbish and carries germs on its legs and mouth from filth to food. That makes it a carrier (vector), not a parasite.

On the body (external parasites): tick, louse, bed bug, flea → Inside the body (internal parasites): tapeworm, roundworm, malaria parasite → Carriers of germs: housefly, mosquito

Why the others are wrong

(a) Ticks suck blood — parasites.

(c) Bed bugs suck blood — parasites.

(d) Lice live on the host — parasites.

The trap

Houseflies spread disease, so they feel like parasites. A carrier is not a parasite.

Also know

Houseflies spread typhoid, cholera and dysentery. A mosquito is both: it sucks blood, and it carries the parasites of malaria and filaria.