Answer: A thin membrane.
Explanation:
When a sound signal is allowed to pass through the voice coil suspended between permanent magnet, magnetic field will be induced which will cause vibration in the diaphragm - a thin membrane causing disturbance of air in the surrounding of membranes which eventually produce sound waves.
Therefore, we can conclude that a thin membrane of the loud speaker produces sound waves
2 is B. 3 is D. 4 is C. I think 5 is A. 6 is A. 7 is D. I think you are all correct. Good Luck!
Potential energy
potential energy is the stored energy an object has, the bike is not moving and it just sitting on the hill, with the stored energy