If Ramesh is suffering from Malaria, his disease is classified as ____________ causative disease.

The correct option is Protozoal.

Malaria is an infectious disease caused by microscopic, single-celled eukaryotic organisms known as protozoans. Specifically, it is caused by protozoan parasites belonging to the genus Plasmodium (such as Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale).
These parasites are transmitted to humans through the bites of infected female Anopheles mosquitoes, which act as vectors for the disease.

Let us look at why the other classifications are incorrect:
1. Viral: Viral diseases are caused by viruses (non-living infectious agents consisting of genetic material inside a protein coat), such as Dengue, Influenza, and Common Cold.
2. Bacterial: Bacterial diseases are caused by single-celled prokaryotic bacteria, such as Tuberculosis, Cholera, and Typhoid.
3. Fungal: Fungal diseases are caused by fungi (spore-producing organisms), such as Ringworm and Athlete's foot.

Because the causative agent of Malaria is a protozoan (Plasmodium), Ramesh's illness is classified as a protozoal disease.