What is the advantage in choosing the wavelength of light as a standard of length?

Only 3% of the water on earth is usable by humans. even though that 3% is through the water cycle, we still need to be careful not to waste water.

What type of graph used to show how a part of something relates to the whole

Astudent is concluding an expirinent to determine how far a ball will roll down a ramp based on the angel of incline. what are three possible controls for this expiriment