Question 6 of 10 Which two characteristics make electromagnetic waves effective in
communication?
O A. They carry more energy than visible light.
B. They do not require a medium to carry information.
C. They carry information very quickly.
D. They move faster through matter than through space.

learn it on the intertant so you can solve

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