(b) as the sexual phase of the malarial parasite occurs in the mosquito it is considered the primary host of malarial parasite.

The primary host of malaria is both the female Anopheles mosquito (b) and the Plasmodium parasite (c). Let's explore this in detail:

1. Human Host (a):
The human host plays a crucial role in the life cycle of the malaria parasite. When an infected female Anopheles mosquito bites a human, it injects the sporozoites of the Plasmodium parasite into the bloodstream. These sporozoites travel to the liver and infect liver cells, where they multiply and mature into merozoites.

2. Female Anopheles Mosquito (b):
The female Anopheles mosquito acts as a vector for the transmission of the malaria parasite. When an infected mosquito bites a human, it ingests the gametocytes of the Plasmodium parasite along with the blood. Inside the mosquito, these gametocytes mature into gametes, which fuse and form zygotes.

Within the mosquito's gut, the zygotes develop into ookinetes and then traverse the gut wall to form oocysts on the outer surface. The oocysts release thousands of sporozoites, which migrate to the salivary glands of the mosquito. When the mosquito bites another human, it injects these sporozoites into the bloodstream, starting the infection cycle again.

3. Plasmodium Parasite (c):
The Plasmodium parasite is the causative agent of malaria. It has multiple species, including Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale. These parasites undergo a complex life cycle involving both human and mosquito hosts.

In humans, the parasite undergoes asexual reproduction within liver cells and red blood cells, leading to the symptoms of malaria. In the mosquito, the parasite undergoes sexual reproduction, producing gametocytes that can be transmitted to humans through mosquito bites.

By completing its life cycle within both the human and mosquito hosts, the Plasmodium parasite ensures its survival and propagation.

In conclusion, the primary host of malaria is both the human host and the female Anopheles mosquito. The human host provides a suitable environment for the parasite to reproduce, while the mosquito acts as a vector for the transmission of the parasite from one human to another. Understanding the role of both hosts is crucial in developing effective strategies for malaria prevention and control.