Which of the following will decrease the density of population in a given area ?

Options

A. Nataility and Immigration
B. Mortality and Immigration
C. Natality and Emigration
D. Mortality and Emigration

Explanation

To determine which factors will decrease the density of a population in a given area, we need to analyze the options provided in the question. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understand the Terms
- **Natality**: This refers to the number of births in a population over a specific period. An increase in natality means more individuals are added to the population, which would increase population density.
- **Immigration**: This is the movement of individuals into a population from another area. Immigration increases the number of individuals in the population, thus increasing density.

### Step 2: Analyze the First Option (Natality and Immigration)
- Since both natality and immigration lead to an increase in the number of individuals in the population, this option will not decrease the population density.

### Step 3: Understand Mortality
- **Mortality**: This refers to the number of deaths in a population over a specific period. An increase in mortality means more individuals are leaving the population, which would decrease population density.

### Step 4: Analyze the Second Option (Mortality and Immigration)
- Here, mortality decreases population density, but immigration increases it. Therefore, this combination does not guarantee a decrease in population density.

### Step 5: Understand Emigration
- **Emigration**: This is the movement of individuals out of a population to another area. Emigration decreases the number of individuals remaining in the population, thus decreasing population density.

### Step 6: Analyze the Third Option (Natality and Emigration)
- Natality increases population density, while emigration decreases it. Since one factor increases and the other decreases, this option does not ensure a decrease in population density.

### Step 7: Analyze the Fourth Option (Mortality and Emigration)
- Both mortality and emigration lead to a decrease in the number of individuals in the population. Therefore, this combination will definitely decrease the population density.

### Conclusion
Based on the analysis, the correct answer is **Mortality and Emigration**, as both factors contribute to a decrease in population density.

### Final Answer
**The correct option is: Mortality and Emigration.**

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