**Core Concept**
The risk of molar pregnancy is influenced by several factors, including reproductive history, age, and underlying medical conditions. A molar pregnancy occurs when a non-viable fertilized egg implants in the uterus, leading to an abnormal growth that can cause complications.

**Why the Correct Answer is Right**
Advanced age is a significant risk factor for molar pregnancy. As women age, the likelihood of chromosomal abnormalities in the fertilized egg increases, which can lead to the development of a molar pregnancy. This is because older women are more likely to have eggs with chromosomal abnormalities, such as triploidy (three sets of chromosomes) or tetraploidy (four sets of chromosomes), which can result in a molar pregnancy. The risk of molar pregnancy is highest in women over 35 years of age.

**Why Each Wrong Option is Incorrect**
**Option A:** Prior C-section is not a direct risk factor for molar pregnancy. While a history of C-section may increase the risk of subsequent pregnancy complications, it does not specifically contribute to the development of a molar pregnancy.

**Option B:** Hypertension in pregnancy is a risk factor for various complications, including preeclampsia and fetal growth restriction, but it is not a specific risk factor for molar pregnancy.

**Option D:** Diabetes in pregnancy is a risk factor for several complications, including fetal macrosomia and birth defects, but it is not a direct risk factor for molar pregnancy.

**Clinical Pearl / High-Yield Fact**
It's essential to note that women who have had a previous molar pregnancy are at increased risk of developing a subsequent molar pregnancy, particularly if they conceive within a year of the previous pregnancy. This is known as the "molar recurrence risk."

**✓ Correct Answer: C. Advanced age**