The infective form of toxoplasma gondii is-a) Oocystb) Bradycystc) Tachyzoited) All of the above

**Core Concept**
Toxoplasma gondii is a protozoan parasite that has a complex life cycle involving multiple forms. The infective form of the parasite varies depending on the host and the stage of the life cycle. Understanding the different forms of T. gondii is crucial for diagnosis and treatment of toxoplasmosis.

**Why the Correct Answer is Right**
The infective form of T. gondii depends on the host and the stage of the life cycle. In cats, the definitive host, the infective form is the oocyst, which is shed in the feces and can infect other hosts. In humans and other intermediate hosts, the infective form is the tissue cyst (bradyzoite), which is formed when the parasite is ingested or transmitted vertically. However, in the acute phase of the infection, the tachyzoite form is also present and can cause disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** The oocyst is indeed an infective form of T. gondii, but it is specific to the definitive host, cats. It is not the primary infective form in humans.
* **Option B:** The bradyzoite (tissue cyst) is an infective form of T. gondii, but it is specific to the intermediate host, including humans. It is not the primary infective form in cats.
* **Option C:** The tachyzoite is an active form of T. gondii, but it is not the primary infective form. It is typically seen in the acute phase of the infection and can cause disease.

**Clinical Pearl / High-Yield Fact**
Toxoplasmosis can be prevented by avoiding ingestion of undercooked meat, particularly pork and lamb, and by proper handling of cat litter. Pregnant women should take extra precautions to avoid infection, as it can lead to congenital toxoplasmosis.

**Correct Answer: C. Tachyzoite**