**Core Concept**
McEwan's triangle is a significant anatomical landmark in the context of the femoral triangle. It is a smaller triangle within the femoral triangle, bounded by the medial border of the sartorius muscle, the medial border of the adductor longus muscle, and the inguinal ligament. McEwan's triangle is important for the location of the femoral canal, which contains the femoral canal lymph nodes and the lymphatic vessels.

**Why the Correct Answer is Right**
The location of McEwan's triangle is crucial for the identification of the femoral canal, which is a potential space in the femoral sheath. The femoral canal is situated within the medial border of the sartorius muscle and the medial border of the adductor longus muscle, and its contents are significant for the lymphatic drainage of the lower limb. The presence of the femoral canal is a key anatomical feature that is often tested in medical exams.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because McEwan's triangle is not located on the lateral border of the sartorius muscle.
**Option B:** Incorrect because McEwan's triangle is not located on the lateral border of the adductor longus muscle.
**Option C:** Incorrect because McEwan's triangle is not located on the medial border of the sartorius muscle and the lateral border of the adductor longus muscle.

**Clinical Pearl / High-Yield Fact**
McEwan's triangle is an important landmark for surgeons and anesthesiologists, as it is a common site for femoral artery and vein cannulation. Knowledge of the location of McEwan's triangle can help prevent complications such as nerve injury or hematoma.

**Correct Answer:** C