**Core Concept**
The broad ligament is a peritoneal fold that supports the uterus and surrounding structures. It is a key anatomical component of the female reproductive system. The broad ligament has two layers: the anterior layer, which is attached to the uterus, and the posterior layer, which is attached to the pelvic sidewall.

**Why the Correct Answer is Right**
The correct answer is a fold of peritoneum that attaches the uterus to the pelvic sidewall. The broad ligament plays a crucial role in supporting the uterus and surrounding structures, including the ovaries, fallopian tubes, and the ureters. The posterior layer of the broad ligament is attached to the pelvic sidewall, which helps to maintain the position of the uterus and other pelvic organs.

**Why Each Wrong Option is Incorrect**
**Option A:** The round ligament of the uterus is a fibromuscular cord that runs from the uterus to the labia majora. It is not a part of the broad ligament.

**Option B:** The infundibulopelvic ligament is a fold of peritoneum that attaches the ovaries to the pelvic sidewall. It is not a part of the broad ligament.

**Option D:** The cardinal ligaments are fibromuscular structures that provide support to the uterus and cervix. They are not a part of the broad ligament.

**Clinical Pearl / High-Yield Fact**
The broad ligament is a critical anatomical structure that supports the uterus and surrounding organs. It is also an important landmark for surgeons during pelvic surgeries.

**Correct Answer: C. Mesovarium**