**Core Concept**
The Commando operation is a surgical procedure involving the en bloc excision of a primary tumor and its regional lymph nodes, in this case, carcinoma of the tongue, the floor of the mouth, part of the jaw, and surrounding lymph nodes. This approach is typically employed in the management of advanced or aggressive tumors that require wide excision and lymphadenectomy for optimal oncologic outcomes.

**Why the Correct Answer is Right**
The Commando operation is a modified en bloc resection procedure that involves the removal of the primary tumor, along with the surrounding tissue, including part of the jaw and lymph nodes. This comprehensive approach is aimed at achieving complete tumor excision and minimizing the risk of local recurrence. The procedure is often performed in cases of advanced oral cancer, particularly carcinoma of the tongue, which has a high propensity for local invasion and lymph node metastasis. The en bloc excision of the tumor and lymph nodes allows for the removal of the disease in a single surgical step, reducing the risk of residual disease and promoting optimal healing.

**Why Each Wrong Option is Incorrect**
**Option A:** Abdomino-perineal resection of the rectum for carcinoma is a surgical procedure for rectal cancer, not oral cancer, and does not involve the en bloc excision of lymph nodes or jaw tissue.

**Option B:** Disarticulation of the hip for gas gangrene of the leg is a procedure for managing complex infections or trauma, unrelated to the Commando operation.

**Option C:** Extended radical mastectomy involves the removal of the breast, underlying chest muscles, and lymph nodes, which is a procedure for breast cancer, not oral cancer.

**Clinical Pearl / High-Yield Fact**
The Commando operation is a classic example of a composite resection procedure in head and neck surgery, where the primary tumor and regional lymph nodes are removed en bloc to achieve optimal oncologic outcomes. This approach requires meticulous preoperative planning, precise surgical technique, and a thorough understanding of the anatomy and lymphatic drainage of the head and neck region.

✓ Correct Answer: D. Excision of carcinoma of the tongue, the floor of the mouth, part of the jaw and lymph nodes en bloc.