## **Core Concept**
The question tests knowledge of the life cycle of *Plasmodium* species, which cause malaria. The infective stage of malaria parasites transmitted to humans through the bite of an infected female *Anopheles* mosquito is crucial for understanding the disease's pathogenesis.

## **Why the Correct Answer is Right**
The correct answer, **sporozoites**, are the infective stage of malaria parasites injected into human subjects by the mosquito. When an infected mosquito bites a human, it injects sporozoites into the person's bloodstream. These sporozoites then travel to the liver, where they initiate the exo-erythrocytic phase of the malaria life cycle. This phase involves the parasites multiplying in liver cells before being released into the bloodstream to infect red blood cells.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify the correct stage. Without the actual text of option A, we can infer that it likely refers to a different stage of the malaria parasite life cycle.
- **Option B:** Similarly, this option is incorrect for the same reason; it likely refers to another stage such as trophozoites, schizonts, or merozoites, which are not the stages injected by the mosquito.
- **Option D:** This option is also incorrect as it presumably refers to another stage of the parasite's life cycle not transmitted by the mosquito.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **sporozoites** are the stage of *Plasmodium* injected by mosquitoes into humans, marking the beginning of a malaria infection. This stage is critical for initiating the disease process.

## **Correct Answer:** . **Sporozoites**