**Core Concept**
The Indira Gandhi National Disability Pension Scheme (IGNDPS) is a social welfare program in India that provides financial assistance to individuals with disabilities. This scheme is a part of the National Social Assistance Program (NSAP), which aims to provide a safety net for the vulnerable sections of society.

**Why the Correct Answer is Right**
The amount of monthly pension under the Indira Gandhi National Disability Pension Scheme is Rs. 200. This amount is fixed by the government to provide a basic level of financial support to individuals with disabilities, allowing them to maintain a decent standard of living. The pension amount is designed to be sufficient to cover the basic needs of the individual, including food, shelter, and healthcare.

**Why Each Wrong Option is Incorrect**
**Option B:** Rs. 450 - This is incorrect because the specified amount is higher than the actual pension amount under the scheme.
**Option C:** Rs. 500 - This is also incorrect for the same reason as Option B.
**Option D:** Rs. 600 - This is incorrect as it is the highest among the options, but the actual pension amount is much lower.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the pension amount under the Indira Gandhi National Disability Pension Scheme is subject to revision from time to time. Students should be aware of the current pension amount to answer questions related to this scheme accurately.

**✓ Correct Answer: A. Rs. 200**