This is a podcast about airplane contrails. You can listen to this part twice: first straight through and then in short sections. Read the questions carefully and then listen to the recording.

6.1
How are cirrus clouds connected to contrails? (2 p.)

Contrails actually are cirrus clouds
Contrails can develop into cirrus clouds
Contrails are condensed cirrus clouds

6.2
What do contrails consist of? (2 p.)

Water in the form of vapor
Water and condensed particles
Water and dust molecules

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6.3
What sometimes causes airplanes to not leave contrails at all? (2 p.)

Rapid changes in the state of water
Certain air pressure in the atmosphere
High levels of humidity in the air

6.4
Which feature of contrails can be used in weather forecasting? (2 p.)

Their height in the atmosphere
Their visible life span
Their saturation level