Indian Population Blood Group Combination

This question requires identifying the correct statistical combination for blood groups and Rh factor prevalence in the Indian population.

Key Prevalence Data for India

General demographic studies indicate the following approximate prevalence patterns in India:

• Blood Group O: Typically the most common group, with frequencies often ranging from 30\% to 40\%.
• Rh Negative (Rh$^-$): This factor is relatively rare in the Indian population, with prevalence usually estimated between 5\% and 7\%.

Evaluating Provided Options

Comparing the options against this established data:

1. Blood group AB 20%; Rh negative 15%

Incorrect. Blood group AB is generally less than 10% in India, and Rh$^-$ prevalence is typically lower than 15%.

2. Blood group A 40%; Rh positive 80%

Less accurate. While Blood group A is common, 40% might be high. An 80% Rh positive rate implies 20% Rh$^-$ rate, which is significantly higher than the usual prevalence.

3. Blood group O 40%; Rh negative 7%

Correct. This combination closely matches the known high frequency of Blood group O (around 40\%) and the low frequency of Rh$^-$ (around 7\%) in the Indian population.

4. Blood group B 33%; Rh positive 99%

Less accurate. While Blood group B frequency can be around 33%, a 99% Rh positive rate implies only 1% Rh$^-$ prevalence, which is exceptionally low.

Option 3 offers the most statistically sound representation based on common findings in Indian population studies.