**Core Concept**
A transverse lie in labor refers to a fetus that is positioned obliquely across the mother's abdomen, rather than in a head-down or feet-down position. This can make vaginal delivery difficult and increases the risk of complications. The primary goal in managing a transverse lie is to achieve a more favorable fetal position to facilitate a safe and successful delivery.

**Why the Correct Answer is Right**
The treatment of choice for a transverse lie in labor is usually a cesarean section (C-section). This is because a C-section allows for a controlled and safe delivery, minimizing the risk of complications such as umbilical cord prolapse, placental abruption, or fetal distress. In a C-section, the obstetrician can surgically remove the baby from the uterus, which is often necessary in cases of a transverse lie.

**Why Each Wrong Option is Incorrect**
**Option A:** External cephalic version (ECV) is a procedure where a healthcare provider tries to manually turn the fetus from a transverse lie to a head-down position. However, ECV is typically attempted before labor begins and is not a viable option in active labor. Additionally, ECV carries a risk of complications, such as placental abruption or umbilical cord prolapse, which makes it a less desirable option in this scenario.

**Option B:** Vaginal delivery is not a suitable option for a transverse lie in labor due to the increased risk of complications. Attempting a vaginal delivery in this scenario may put the mother and baby at risk of serious harm.

**Option C:** Artificial rupture of membranes (AROM) is a procedure where the healthcare provider breaks the water to induce labor. However, AROM is not a treatment for a transverse lie and may not address the underlying issue.

**Clinical Pearl / High-Yield Fact**
In cases of a transverse lie, it's essential to monitor the mother's and baby's condition closely, as complications can arise quickly. A timely C-section can help prevent serious complications and ensure a safe delivery for both mother and baby.

**Correct Answer:** C. Cesarean section.