Characteristic feature of amoebic ulcer -a) Flask shapedb) Undermined edgesc) Rolled up edged) Punched out

**Core Concept**
The characteristic feature of an amoebic ulcer is related to the pathophysiology of the disease caused by **Entamoeba histolytica**, which involves the invasion of the intestinal mucosa and the formation of ulcers.

**Why the Correct Answer is Right**
The correct answer is related to the appearance of the ulcer, which is a result of the amoeba's invasion and the subsequent immune response. The **flask-shaped** ulcer is characteristic due to the way the amoeba burrows into the tissue, creating a narrow neck and a wider base. This shape is a result of the **lytic enzymes** produced by the amoeba, which break down the tissue.

**Why Each Wrong Option is Incorrect**
**Option B:** Undermined edges are not a characteristic feature of amoebic ulcers. **Option C:** Rolled up edges are more typical of certain types of malignant ulcers. **Option D:** Punched out ulcers can be seen in other conditions, but are not specific to amoebiasis.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that amoebic ulcers are often **painless**, which can distinguish them from other types of ulcers. The **flask-shaped** appearance is a classic description in medical literature.

**Correct Answer:** A. Flask shaped