**Core Concept**
Entamoeba histolytica is a protozoan parasite that causes amoebiasis, a disease characterized by gastrointestinal symptoms and potentially life-threatening complications. The infective form of E. histolytica is crucial for its transmission and establishment of infection in humans.

**Why the Correct Answer is Right**
The infective form of E. histolytica is the cyst, which is highly resistant to environmental stress and can survive outside the human body for several days. The cysts are ingested through contaminated food or water, and once inside the human body, they transform into trophozoites, the active and pathogenic form of the parasite. The cysts contain four nuclei, which is a key feature for identification.

**Why Each Wrong Option is Incorrect**
**Option A:** The trophozoite form of E. histolytica is pathogenic, but it is not the infective form of the parasite. Trophozoites are found in the lumen of the intestine and are responsible for the clinical manifestations of amoebiasis.
**Option B:** The term "amoeba" is a general term for a type of protozoan, but it is not specific to E. histolytica or its infective form. All amoebas have a single nucleus, whereas the infective form of E. histolytica is characterized by four nuclei.
**Option C:** The term "amoebic dysentery" is a clinical manifestation of amoebiasis, but it is not the infective form of E. histolytica. Amoebic dysentery is a symptom complex characterized by diarrhea, abdominal pain, and blood in the stool.

**Clinical Pearl / High-Yield Fact**
The infective form of E. histolytica, the cyst, can be identified by its characteristic four nuclei. This feature is essential for the laboratory diagnosis of amoebiasis.

**Correct Answer:** C.