Malaria transmission agent and role

Steps:

• Identify the disease: Malaria is caused by Plasmodium parasites.
• Recall transmission: It spreads via bites from infected female Anopheles mosquitoes.
• Define key terms: A vector is an organism that carries and transmits a pathogen without causing disease itself.
• Match to sentence: The mosquito spreads malaria and acts as its vector.

Why D is correct:

• "Vector" is the epidemiological term for an animal (like a mosquito) that transmits a disease pathogen, as defined by the CDC and WHO.

Why the others are wrong:

• A: Malaria is caused by a parasite, not a bacterium; bacteria cause diseases like cholera.
• B: Choice is incomplete and provides no valid terms.
• C: Mosquito is correct, but "parasite" refers to the Plasmodium causing malaria, not the mosquito's role.

Final answer: D