Aeroplanes usually fly in the stratosphere because

Options

A. of the presence of ozone layer.
B. of the atmosphere being turbulent.
C. of the decrease in temperature with altitude.
D. of the absence of convection current.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Stratosphere:**
- The stratosphere is the second layer of Earth's atmosphere, located above the troposphere and below the mesosphere. It extends from about 10 to 50 kilometers above the Earth's surface.

2. **Characteristics of the Stratosphere:**
- The stratosphere has a stable atmosphere with very little turbulence compared to the lower layer (troposphere). This stability is crucial for the smooth operation of aircraft.

3. **Presence of the Ozone Layer:**
- The stratosphere contains the ozone layer, which absorbs and scatters ultraviolet solar radiation. This is important for protecting both the aircraft and passengers from harmful UV rays.

4. **Fuel Efficiency:**
- Flying at higher altitudes, such as in the stratosphere, allows airplanes to take advantage of thinner air, which reduces drag and increases fuel efficiency.

5. **Avoiding Weather Disturbances:**
- Most weather phenomena, such as storms and turbulence, occur in the troposphere. By flying in the stratosphere, airplanes can avoid these disturbances, leading to a smoother flight experience.

6. **Conclusion:**
- Therefore, aeroplanes usually fly in the stratosphere because it provides a stable environment, protects against UV radiation, enhances fuel efficiency, and helps avoid weather-related issues.