**Question:** Sex ratio is

* Sex ratio refers to the comparison of male to female births or deaths in a specific population or time period.
* The correct answer is the number of males divided by the number of females, expressed as a ratio.

**Correct Answer:** Sex ratio is calculated as (number of males) / (number of females)

**Core Concept:**
Sex ratio is determined by the balance between male and female births, deaths, and migration within a population. Factors that influence sex ratios include genetics, environmental conditions, and social practices. For example, in some societies, male infants are preferred due to cultural or economic factors, leading to skewed sex ratios.

**Why the Correct Answer is Right:**
The correct answer, (number of males) / (number of females), represents the division of the number of males by the number of females, resulting in a ratio. This ratio is crucial for understanding the balance between the sexes within a population and can provide insights into potential health and demographic implications.

**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because dividing by a fraction would result in an undefined value.
B. This option is incorrect as it does not represent the division of males by females.
C. This option is incorrect because it does not represent the division of males by females but rather a simple multiplication.
D. This option is incorrect as it involves dividing by zero, which leads to an undefined value.

**Clinical Pearl:**
The understanding of sex ratios is essential for healthcare professionals to predict and address the potential health and demographic implications of imbalanced ratios. These implications can include increased rates of genetic disorders in children, increased maternal and infant mortality, and increased social and economic pressures on families with more daughters than sons. By recognizing and understanding these trends, healthcare professionals can help plan public health interventions and policies to address these issues.