High birth rate makes this country seriously ______.underestimatedoverpopulatedilliteratesimplified

The correct answer to fill in the blank is "overpopulated."

Explanation:

A high birth rate often leads to an increase in the population size relative to the resources available, which can result in various challenges such as housing shortages, strains on social services, and environmental degradation. "Overpopulated" accurately describes a situation where the number of people exceeds the capacity of the environment to support them, especially in terms of sustainable living conditions.

In contrast:

• "Underestimated" implies a miscalculation or undervaluation, which does not directly relate to the concept of birth rates.
• "Illiterate" refers to a lack of education, which is not a direct consequence of high birth rates.
• "Simplified" refers to something made easier or less complex, which doesn’t apply in this context.

Therefore, the most suitable word is "overpopulated."