**Core Concept**
Amoebic liver abscess is a complication of amoebiasis, caused by the protozoan parasite *Entamoeba histolytica*. The diagnosis of amoebic liver abscess relies on a combination of clinical findings, imaging studies, and laboratory tests.

**Why the Correct Answer is Right**
The correct answer is based on the presence of cysts or trophozoites of *E. histolytica* in the liver abscess material. This can be demonstrated through microscopy, either by wet mount or by staining the sample with a dye such as iodine or methylene blue. The presence of these organisms confirms the diagnosis of amoebic liver abscess. **Option A** is the correct answer because it directly demonstrates the causative agent of the disease.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect because it refers to the presence of pus, which is a general finding in abscesses, not specific to amoebic liver abscess. **Option C:** This option is incorrect because it refers to the presence of antibodies, which may not be present in all cases of amoebic liver abscess. **Option D:** This option is incorrect because it refers to the presence of a specific type of cell, which is not a reliable method for diagnosing amoebic liver abscess.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the diagnosis of amoebic liver abscess can be challenging, and a high index of suspicion is required. A history of travel to endemic areas, diarrhea, and abdominal pain should raise the suspicion of amoebiasis.

**Correct Answer: A.**