How is AU different from a solar mass? A. An AU is the distance from the black hole at the center of the galaxy to the closest planet, and solar mass represents a measurement equal to the mass of a black hole's quasar.
B. An AU is the smallest unit of measurement in quantum mechanics, and a solar mass is the largest unit of measurement in astronomy.
C. An AU is the distance from the event horizon to the singularity of a black hole, and solar mass is the distance between the two closest black holes in a galaxy.
D. An AU is the distance from the earth to the sun, and solar mass represents a measurement equal to the mass of our sun.

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.

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