Population Geography

We need to identify the correct definition of "sex ratio."

Step 1: Understand the term "sex ratio."
Sex ratio is a demographic concept used to describe the balance between males and females in a population. It is typically expressed as the number of females per 1000 males or sometimes as the number of males per 100 females, depending on the context and country.

Step 2: Recall the standard definition.
In demography and population studies, sex ratio is defined as:
- The ratio of males to females in a population
- Or more commonly in India, the number of females per 1000 males
The key point is that it compares the number of men and women in the population.

Step 3: Evaluate each option.
- (A) Number of adults in the population — Incorrect. This refers to the adult population, not the ratio between sexes.
- (B) The ratio between the number of men and women in the population — Correct. This accurately defines sex ratio.
- (C) The ratio of the number of children in the population — Incorrect. This refers to child population ratio, not sex ratio.
- (D) Number of males in the population — Incorrect. This is just the male population count, not a ratio.

Step 4: Conclusion.
Sex ratio means the ratio between the number of men and women in the population.
Final Answer: (B) The ratio between the number of men and women in the population