**Core Concept**
Ectopic pregnancy occurs when a fertilized ovum implants outside the uterine cavity, most commonly in the fallopian tube. This condition is a life-threatening emergency that requires prompt medical attention. The pathophysiology involves hormonal imbalances and anatomical abnormalities that disrupt normal ovum transport and implantation.

**Why the Correct Answer is Right**
The correct answer is related to the clinical presentation and diagnosis of ectopic pregnancy. Ectopic pregnancy often presents with abdominal pain, amenorrhea, and positive pregnancy test, but beta-hCG levels may not rise as expected. **Option C** is likely the correct answer, as beta-hCG levels in ectopic pregnancy may not double as quickly as in normal intrauterine pregnancy, making it a crucial diagnostic clue.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might refer to the use of methotrexate in treating ectopic pregnancy, but it's not the correct answer.

**Option B:** While ectopic pregnancy can present with hemoperitoneum, it's not the definitive diagnostic feature.

**Option D:** This option is incorrect as it's not a characteristic of ectopic pregnancy.

**Clinical Pearl / High-Yield Fact**
A classic clinical pearl for diagnosing ectopic pregnancy is the "Double Decidual Sign" on ultrasound, which is a specific sign of an intrauterine gestation. However, in the setting of ectopic pregnancy, the ultrasound findings may be inconclusive, and a high index of suspicion is required.

**Correct Answer: C**. Beta-hCG levels in ectopic pregnancy may not double as quickly as in normal intrauterine pregnancy.