Malaria pathogen classification Steps:

• Identify the disease: Malaria is a human infection transmitted by mosquitoes.
• Recall the causative agent: The pathogen is Plasmodium, a single-celled organism that invades red blood cells.
• Classify the organism: Plasmodium belongs to the protozoa group, which are eukaryotic parasites.
• Match to options: Compare with choices to find the best descriptor.

Why B is correct:

• Parasite defines Plasmodium as an organism that lives in a host and causes harm, fitting the biological classification of protozoan parasites.

Why the others are wrong:

• A: Bacteria are prokaryotic cells like E. coli; Plasmodium is eukaryotic.
• C: Insects are animals like mosquitoes, which transmit but do not cause malaria.
• D: Vector refers to the carrier (mosquito), not the pathogen itself.

Final answer: B