Metre
Metre.
use your brain to count
The SI unit used to measure length or distance is the meter (m).
The standard unit used to measure sound power is the decibel (dB).
light years
Angstroms
A unit of measure is an officially standard used to make measurements.
Because that is the standard unit of distance used in the US.
meter
Kilometers are a unit of length, used to measure distance.
degrees, minutes and seconds. (and radians are also a standard unit of angular measure).
Meters or kilometers, depending on the distance.