## **Core Concept**
The sex ratio is defined as the number of females per 1000 males in a population. It is an important demographic measure used to understand the balance between the male and female populations.

## **Why the Correct Answer is Right**
Given that the city has a population of 10,000 with an equal number of males and females, there are 5,000 males and 5,000 females. The sex ratio is calculated as the number of females per 1000 males. Therefore, the sex ratio = (5,000 / 5,000) * 1000 = 1000.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the calculation or definition of sex ratio.
- **Option B:** This option is incorrect because, similar to option A, it does not correctly represent the sex ratio calculation based on the given population data.
- **Option D:** This option is incorrect because it suggests a different ratio that does not align with the equal distribution of males and females provided in the question.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that a sex ratio of 1000 indicates an equal number of females and males. This demographic measure is crucial in epidemiology and public health for understanding population dynamics and planning healthcare services.

## **Correct Answer:** . 1000.