In the context of the Census of India, which of the following correctly describes the term sex ratio?

Introduction / Context:
Sex ratio is an important demographic indicator used in population studies and social policy, particularly in a country like India where gender balance is a key concern. It reflects the relative number of females and males in a population and can highlight social issues such as gender preference, discrimination, or differences in mortality. This question asks for the precise definition of sex ratio as used in the Census of India, which follows a specific convention.

Given Data / Assumptions:

• Options present different ways of expressing the ratio of males and females.
• We assume the official Indian practice for defining sex ratio.
• The usual base for sex ratio in India is 1000.
• We are asked to choose the correct numerical relationship between the number of females and the number of males.

Concept / Approach:
In the Indian census context, sex ratio is defined as the number of females per 1000 males. This means that if the sex ratio is 950, there are 950 females for every 1000 males in the population. Other possible ways of expressing gender balance, such as number of males per 1000 females, are used in some other countries, but the Indian convention is firmly based on females per 1000 males. It is important to recall this specific convention when answering such questions.

Step-by-Step Solution:
Step 1: Recall that the Census of India defines sex ratio as the number of females per 1000 males.Step 2: Match this definition with the given options.Step 3: Option B states "Number of females per 1000 males," which matches exactly.Step 4: Option A reverses the ratio and refers to the number of males per 1000 females, which is not the standard Indian practice.Step 5: Option C uses a base of 100 males, which is not the official convention in India.Step 6: Option D refers to the number of females in a sample of 1000 persons, which is a different measure and not the definition of sex ratio.Step 7: Therefore, the correct definition is given by option B.

Verification / Alternative check:
Official publications of the Census of India, as well as National Family Health Surveys and other demographic reports, express sex ratio as females per 1000 males. For example, if a report says the sex ratio is 940, it means there are 940 females for every 1000 males. This consistent usage confirms that option B is the correct answer. If the definition were males per 1000 females, the reported figures would have a completely different interpretation, which is not how Indian data is presented.

Why Other Options Are Wrong:
Option A is wrong because it reverses the roles of males and females and defines the ratio differently from the Indian convention. Option C is incorrect because it uses a base of 100 males instead of 1000, which is not standard practice in Indian census data. Option D is wrong because it describes a different kind of statistic, not a ratio between males and females via a fixed number of one group. Thus only option B aligns with the official Indian definition of sex ratio.

Common Pitfalls:
Students may be familiar with other countries or studies where sex ratio is expressed as males per 100 females and may accidentally apply that convention to India. Another pitfall is to think of sex ratio in terms of percentages or overall counts rather than a clear ratio with a fixed base. Remembering the phrase "females per 1000 males" as a fixed expression for Indian data helps avoid confusion.

Final Answer:
In the Census of India, sex ratio is defined as the Number of females per 1000 males.