Select the correct answer. Light ray A moves from air to water. Part of ray A is reflected at the air-water boundary. Which arrow in the image is the reflected ray?
A
ВА
E
O A А. В
OB. C
O CD
OD
E

i think the answer is a, hope this : )

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me