Which of the following parasites feed on external surface of host organism ?

Ecto parasites

The correct answer is Option (1) -  Ectoparasites

Explanation:

• Ectoparasites live on the external surface of the host and feed on it (e.g., ticks, lice, fleas).
• Endoparasites live inside the host's body (e.g., tapeworms, malaria parasite).
• Brood parasites rely on other species to raise their young (e.g., cuckoo birds), but they do not necessarily feed on the host.

Since the question asks about parasites that feed on the external surface, the correct choice is Ectoparasites.