**Core Concept**
Toxoplasmosis is a parasitic infection caused by the protozoan *Toxoplasma gondii*. The oocyst is a stage in the life cycle of the parasite, which is crucial for its transmission.

**Why the Correct Answer is Right**
The oocyst of *Toxoplasma gondii* is typically found in the feces of infected domestic cats (Felidae family). When a cat ingests infected tissue or oocysts, the parasites undergo asexual multiplication in the cat's intestinal epithelial cells, and eventually form oocysts. These oocysts are then shed in the cat's feces, which can contaminate soil, water, and other surfaces. Humans can become infected by ingesting contaminated food or water, or through accidental ingestion of oocysts from contaminated soil.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because oocysts are not typically found in the urine of infected individuals.
**Option B:** Incorrect because oocysts are not found in the blood of infected individuals; the tachyzoite stage is present in the bloodstream during acute infection.
**Option C:** Incorrect because oocysts are not found in the tissues of intermediate hosts (such as mice); the cyst stage is present in these hosts.

**Clinical Pearl / High-Yield Fact**
It's essential to note that cats are the definitive hosts of *Toxoplasma gondii*, and they can shed oocysts in their feces for several weeks after infection. Pregnant women should avoid changing cat litter to prevent accidental ingestion of oocysts.

**Correct Answer: D. Feces of infected domestic cats.**