the electrical charge of the sound waves the direction in which the sound waves travel the amount of energy released by each sound wave the type of material through which the sound travels
I gave my students this multiple choice question: Light waves travel faster than sound waves, so a lightning bolt can be seen before the thunder is heard. Which factor can also affect how quickly thunder is heard?

Only one answer is correct among these 4 choices:
- the electrical charge of the sound waves
- the direction in which the sound waves travel
- the amount of energy released by each sound wave
- the type of material through which the sound travels

Could you tell me which one is correct?

the type of material through which the sound travels