**Core Concept**
Molar pregnancy is a gestational trophoblastic disease characterized by the abnormal proliferation of trophoblast cells, resulting in a non-viable pregnancy. This condition is often associated with hormonal imbalances and can lead to complications such as excessive bleeding and hyperglycemia.

**Why the Correct Answer is Right**
Molar pregnancy is typically diagnosed through ultrasound and serum beta-hCG levels. The presence of a characteristic "snowstorm" appearance on ultrasound, along with high beta-hCG levels, is highly suggestive of a molar pregnancy. This is due to the abnormal proliferation of trophoblast cells, which produce excessive amounts of human chorionic gonadotropin (hCG). The high levels of hCG can be detected through serum beta-hCG tests, which are often used in conjunction with ultrasound to confirm the diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because molar pregnancy is not typically diagnosed through physical examination alone.
**Option B:** This option is incorrect because while molar pregnancy can be associated with vaginal bleeding, it is not the most common or definitive diagnostic feature.
**Option C:** This option is incorrect because while serum beta-hCG levels are used in the diagnosis of molar pregnancy, they are not the sole diagnostic criterion.

**Clinical Pearl / High-Yield Fact**
A key aspect of molar pregnancy is the presence of high levels of beta-hCG, which can be used to monitor treatment response and detect any potential complications. It is essential to note that molar pregnancy can be a precursor to more serious conditions such as gestational trophoblastic neoplasia (GTN), which requires prompt and aggressive treatment.

**Correct Answer:** D. Serum beta-hCG levels and ultrasound examination.