Option 1: Ionosphere - This layer of the atmosphere is located above the mesosphere and contains ions and free electrons. It is responsible for the reflection and transmission of radio waves.

Option 2: Mesosphere - This layer is located above the stratosphere and contains very low levels of water vapor and dust particles. It is also where meteoroids burn up upon entering the Earth`s atmosphere.

Option 3: Stratosphere - This layer is located above the troposphere and contains the ozone layer, which absorbs a significant amount of the sun`s ultraviolet radiation. It has very low levels of water vapor and dust particles.

Option 4: Troposphere - This is the lowest layer of the atmosphere, where weather occurs. It contains the majority of Earth`s water vapor and dust particles. The temperature generally decreases with increasing altitude in this layer.

Therefore, the correct answer is option 4 (Troposphere), as it is the layer of the atmosphere that contains water vapor and dust particles.