Question

what type of energy transfer occurs when a helicopter is flying in the air?
the chemical energy from the fuel is transformed into mechanical and sound energy.
the electrical energy from the fuel is transformed into solar and nuclear energy.
the nuclear energy from the fuel is transformed into electromagnetic and electrical energy.

Explanation:

Fuel in a helicopter undergoes combustion. Chemical energy in fuel is converted. Mechanical energy makes it fly (movement). Sound energy is from engine noise etc. Electrical energy isn't from fuel here (fuel is chemical). Nuclear energy is from nuclear reactions (not fuel in regular chopper). Solar energy is from sun (not fuel).

Answer:

The chemical energy from the fuel is transformed into mechanical and sound energy.