Which of the following disease is caused by protozoan?

The correct answer is Option (3) → Malaria

Option (3) Malaria — Correct. Malaria is caused by Plasmodium, a protozoan (P. vivax, P. malaria, P. falciparum). It is spread by the female Anopheles mosquito.

NCERT Extract:
Common Diseases in Humans – “… Some of the human diseases are caused by protozoans too. You might have heard about malaria, a disease man has been fighting since many years. Plasmodium, a tiny protozoan is responsible for this disease. Different species of Plasmodium (P. vivax, P. malaria and P. falciparum) are responsible for different types of malaria. Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal.”