**Core Concept**
The National Maternity Benefit scheme is a government initiative aimed at providing financial assistance to pregnant women, particularly those from Below Poverty Line (BPL) households, to support their well-being and the health of their newborns.

**Why the Correct Answer is Right**
The scheme provides a financial assistance of Rs. 5,000 per birth for the first two births to all pregnant women who attain 19 years of age and belong to BPL households. This assistance is intended to help alleviate the financial burden associated with childbirth and enable women to focus on their health and the health of their newborns. The amount of Rs. 5,000 is a one-time payment made to the woman's bank account, which can be used to cover various expenses related to childbirth, including medical fees, food, and other necessities.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the scheme does not provide financial assistance for the first two births to all pregnant women, regardless of age or socioeconomic status.
**Option B:** This option is incorrect because the amount of financial assistance provided under the scheme is not Rs. 10,000, but rather Rs. 5,000 per birth.
**Option C:** This option is incorrect because the scheme is not limited to women who attain 21 years of age, but rather 19 years of age.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the National Maternity Benefit scheme is a government initiative aimed at reducing maternal and infant mortality rates, particularly in BPL households. The scheme's benefits are available to all pregnant women who meet the eligibility criteria, and it's crucial for healthcare providers to be aware of the scheme's details to ensure that eligible women receive the necessary support.

**Correct Answer: D. Rs. 5,000**