Malaria parasites that cause deadly malaria are (b) Plasmodium falciparum. This species is responsible for the majority of severe malaria cases and deaths globally, making it the deadliest of the malaria parasites. Plasmodium falciparum can lead to severe complications such as cerebral malaria, organ failure, and death, particularly in young children and pregnant women. While other species like Plasmodium vivax (c) and Plasmodium malariae (a) can cause malaria, they typically result in milder forms of the disease. Plasmodium ovale (d) is another species but is less common and usually causes less severe symptoms compared to P. falciparum.