**Question:** Infective form of Plasmodium falciparum in mosquito is -

A. Sporozoite
B. Erythrocytic stage
C. Gametocyte
D. Liver stage

**Core Concept:**
Plasmodium falciparum is a protozoan parasite that causes severe malaria in humans. The life cycle of P. falciparum involves multiple stages, including an infective stage in the mosquito vector. In this question, we are focusing on the stage of the parasite that resides in the mosquito and is transmitted to humans upon a bite.

**Why the Correct Answer is Right:**
The correct answer is A. Sporozoite. A sporozoite is the infective form of Plasmodium falciparum found within the salivary glands of the Anopheles mosquito after it feeds on an infected human. When the mosquito bites a new human host, it injects the sporozoites into the bloodstream, where they can invade liver cells and initiate the liver stage of the parasite's life cycle.

**Why Each Wrong Option is Incorrect:**

B. Erythrocytic stage: This refers to the stage of the parasite that infects red blood cells (RBCs) and causes the clinical symptoms of malaria. It is not the correct answer because the question asks for the form that resides in the mosquito.

C. Gametocyte: Gametocytes are the sexual forms of Plasmodium parasites that develop in the mosquito midgut, not the infective form.

D. Liver stage: The liver stage is the form that develops within hepatocytes, not the form found in the mosquito. It is incorrect because the question asks for the form in the mosquito.

**Clinical Pearl:**
Understanding the life cycle of Plasmodium falciparum is essential for understanding the transmission of malaria between humans and mosquitoes. Knowledge of the infective form (sporozoite) in mosquitoes is crucial for preventing malaria transmission and implementing targeted mosquito control measures.