Vector vs. Parasite in Malaria Transmission Steps:

• Define vector as the organism transmitting a pathogen between hosts.
• Recognize female Anopheles mosquito bites infected humans, ingests Plasmodium, and injects it into new hosts via saliva.
• Define parasite as the disease-causing organism that invades and harms the host.
• Identify malaria pathogen as Plasmodium species, which replicates in human blood and liver cells.

Why B is correct:

• Female mosquito serves as vector by mechanically and biologically transmitting Plasmodium; the pathogen is the parasite that infects and causes malaria symptoms.

Why the others are wrong:

• A: Mosquito is not a parasite—it doesn't live off the host but transmits externally.
• C: Reverses roles; Plasmodium is the parasite, not a vector.
• D: Pathogen cannot be a vector; it is the infectious agent, not the carrier.

Final answer: B