Convection is the transfer of heat energy via: 1.plasmas
2.solids or plasmas
3.solids
4.liquids or gases

The answer is option 4.

Explanation:

Convection is the transfer of heat energy through liquid and gas.

Conduction is the transfer of heat energy through solid.

Radiation is the transfer of heat energy through gas(air).

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

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