Which of the following factors have harmful effect on our environment?
Environmental pollution
Natural environmental gases
Uncontrolled birth rate
The correct option (s) is/are

Options

A. II and III
B. Only I
C. I and III
D. Only III

Answer

To determine which factors have harmful effects on our environment, let's analyze each option provided in the question:

1. **Environmental Pollution**:
- Environmental pollution refers to the introduction of harmful substances or pollutants into the environment. This can include air pollution, water pollution, soil contamination, and more. Pollution has detrimental effects on ecosystems, human health, and the overall balance of nature. Therefore, this factor does have a harmful effect on our environment.

2. **Natural Environmental Gases**:
- Natural environmental gases, such as oxygen, nitrogen, and carbon dioxide, are essential components of the Earth's atmosphere. While certain gases can contribute to greenhouse effects when present in excess (like carbon dioxide), they are not inherently harmful in their natural state. Thus, natural environmental gases do not have a harmful effect on our environment.

3. **Uncontrolled Birth Rate**:
- An uncontrolled birth rate can lead to overpopulation. As the population increases, the demand for resources (such as food, water, and energy) also rises. If the population grows faster than the resources can be replenished, it can lead to resource depletion, habitat destruction, and increased waste, all of which have harmful effects on the environment. Therefore, this factor is harmful to our environment.

Based on the analysis:
- Environmental pollution (1) is harmful.
- Natural environmental gases (2) are not harmful.
- Uncontrolled birth rate (3) is harmful.

Thus, the correct options that have harmful effects on our environment are **1 and 3**.

### Final Answer:
The correct option(s) is/are **1 and 3**.