## **Core Concept**
Toxoplasmosis is a parasitic infection caused by *Toxoplasma gondii*. The lifecycle of *T. gondii* involves both definitive and intermediate hosts. Oocysts are a critical part of the lifecycle, particularly in the definitive host, while pseudocysts (or tissue cysts) are important in intermediate hosts.

## **Why the Correct Answer is Right**
The correct answer involves understanding where oocysts and pseudocysts are typically found. Oocysts are shed in the feces of the definitive host, which is usually a cat. Pseudocysts, on the other hand, are found in the tissues of intermediate hosts, which can include humans, birds, and other animals. In humans, pseudocysts can form in various tissues, including the brain, muscles, and eyes, and are a key feature of chronic toxoplasmosis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option incorrectly identifies the locations for oocysts and pseudocysts. Without specific details on A, we can infer it's incorrect based on the correct answer.
- **Option B:** Similarly, B is incorrect as it does not accurately represent the correct locations for oocysts and pseudocysts.
- **Option D:** This option is incorrect because it misidentifies the host or location for oocysts and pseudocysts.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that *Toxoplasma gondii* oocysts are shed in the feces of cats, making cat owners or individuals handling cat litter at risk. Additionally, congenital transmission from mother to fetus can occur if a woman becomes infected during pregnancy. Serological testing is commonly used to diagnose toxoplasmosis.

## **Correct Answer:** C. Cat, Human.