All of the above are correct. Both ancient and modern volcanoes emit water vapor. All of the above are correct. Most atmospheric aerosols originate at Earth's surface. are products of photosynthesis. The source of atmospheric nitrogen is decay of organic matter.
Most water vapor occurs in the troposphere.
The atmospheres of Mars and Venus are composed of mostly water vapor. The transition zone between the stratosphere and mesosphere is known as the thermopause. Remote sensing of the atmosphere is by satellite. All of the above are correct. Most clouds are confined to the troposphere.