When We Say That the Speed of Sound Is Measured

When we say that the speed of sound is measured under adiabatic conditions we assume that

A) the time associated with heat conduction is slow relative to the speed of the wave.
B) no heat can flow between the system and its surroundings.
C) the speed of the wave is directly proportional to the bulk modulus.
D) the speed of the wave is proportional to the square root of the bulk modulus.
E) air is an ideal gas.