When population reaches carrying capacity :

Options

A. Mortality rate =birth rate
B. Mortality rate `gt` birth rate
C. Mortality `lt` birth rate
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Carrying Capacity**:
- Carrying capacity refers to the maximum population size of a species that an environment can sustain indefinitely without degrading the environment. This includes the availability of resources such as food, water, and habitat.

2. **Population Dynamics**:
- In ecology, the dynamics of a population are influenced by birth rates (the number of births in a population) and mortality rates (the number of deaths in a population).

3. **Equilibrium at Carrying Capacity**:
- When a population reaches its carrying capacity, it achieves a state of equilibrium. This means that the number of individuals being born (birth rate) is equal to the number of individuals dying (mortality rate).

4. **Analyzing the Options**:
- **Option A**: Mortality rate is equal to birth rate. This is correct because at carrying capacity, the population stabilizes.
- **Option B**: Mortality rate greater than birth rate. This is incorrect because if mortality exceeds birth, the population would decline, not stabilize.
- **Option C**: Mortality rate less than birth rate. This is also incorrect because if birth exceeds mortality, the population would grow beyond carrying capacity.
- **Option D**: None of the above. This is incorrect since we have identified that Option A is correct.

5. **Conclusion**:
- Therefore, the correct answer is that when a population reaches carrying capacity, the mortality rate is equal to the birth rate.

### Final Answer:
**The correct answer is: Mortality rate is equal to birth rate.**

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