When a sound wave encounters a barrier, what happens?

20. threshold braking in the vehicle's braking system occurs when a. the brake pedal is pushed, heel on floorboard, with full foot pressure. b. the brakes are exerting full braking power, without traction loss. c. the driver begins pushing down the brake pedal, with moderate slowdown. d. the brakes just begin to take hold with a gradual slowdown.

With physics question #5? for any !

Ineed to answer this problem but i lack in knowledge, what should i study to answer this problem? i have never used derivatives in a physics problem so i'm not sure what's happening and i can't find videos explaining.