**Core Concept**
The external oblique muscle is a superficial abdominal muscle that forms the anterior wall of the abdominal cavity. It is involved in various anatomical structures, including the inguinal canal and the superficial inguinal ring.

**Why the Correct Answer is Right**
The correct answer involves three structures associated with the external oblique muscle: the lacunar ligament, the superficial inguinal ring, and the conjoint tendon. The lacunar ligament, also known as Gimbernat's ligament, is a fibrous structure that arises from the inguinal ligament and is attached to the pectineal line of the pubic bone. It is often considered the medial boundary of the femoral canal. The superficial inguinal ring is an opening in the external oblique aponeurosis, allowing for the passage of the spermatic cord in males and the round ligament of the uterus in females. The conjoint tendon is a fibrous structure formed by the fusion of the aponeuroses of the internal and external oblique muscles, which plays a crucial role in the formation of the inguinal canal. These structures are all related to the external oblique muscle and its role in the inguinal region.

**Why Each Wrong Option is Incorrect**
* **Option A:** Poupart's ligament is actually the inguinal ligament, which is formed by the external oblique aponeurosis and is not directly associated with the external oblique muscle.
* **Option C:** The cremaster muscle is actually a muscle of the spermatic cord in males, derived from the internal oblique muscle, and is not directly associated with the external oblique muscle. It is involved in the regulation of testicular temperature.
* **Option D:** The conjoint tendon is associated with the external oblique muscle, but the cremaster muscle is not.

**Clinical Pearl / High-Yield Fact**
The external oblique muscle plays a crucial role in the formation of the inguinal canal and the superficial inguinal ring, which are important anatomical structures in the diagnosis and treatment of inguinal hernias.

**✓ Correct Answer: B. abc. Lacunar ligament, Superficial inguinal ring, and Conjoint tendon.**