**Core Concept**
Prophylactic chemotherapy after evacuation of hydatidiform mole (H.Mole) is indicated to prevent the development of gestational trophoblastic neoplasia (GTN), a potential complication of molar pregnancy. The decision to administer prophylactic chemotherapy is based on specific risk factors, including the initial level of human chorionic gonadotropin (hCG) after evacuation, the rate of hCG decrease, and the presence of metastasis.

**Why the Correct Answer is Right**
The correct answer, **D. Nulliparous lady**, is incorrect because nulliparity itself is not a risk factor for developing GTN. Prophylactic chemotherapy is generally recommended for women with high-risk factors, such as an initial hCG level greater than 100,000 IU/L after evacuation, a hCG level greater than 20,000 IU/L after 4 weeks, or the presence of metastasis. Nulliparity is not a specific risk factor that warrants prophylactic chemotherapy.

**Why Each Wrong Option is Incorrect**
**Option A:** An initial level of urine hCG of 40,000 IU after 6 weeks of evacuation is actually a relatively low level, and prophylactic chemotherapy would not be indicated in this case.

**Option B:** An increase in hCG titre of 24,000 IU after 10 weeks of evacuation suggests a possible need for further investigation or treatment, but it is not an absolute indication for prophylactic chemotherapy.

**Option C:** Metastasis is a high-risk factor for developing GTN, and prophylactic chemotherapy is indicated in cases of confirmed metastasis.

**Clinical Pearl / High-Yield Fact**
It is essential to monitor hCG levels regularly after evacuation of a hydatidiform mole to identify high-risk patients who may require prophylactic chemotherapy. A hCG level that remains elevated or increases after 4-6 weeks post-evacuation warrants further investigation and may necessitate treatment.

**✓ Correct Answer: D. Nulliparous lady**