Answer:
D. The distance between two identical points of a wave
Explanation:
Wavelength is the the distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.
You can look at the picture to show wavelength.
<em>Hope this helps!!</em>
<em>- Kay</em>
Answer:
A map usually has a legend, or key, that gives the scale of the map and explains what the various symbols represent. Some maps show relief, or changes in elevation. A common way to show relief is contour lines, also called topographic lines. These are lines that connect points that have equal elevation.
Explanation:
So the people doing it will be safe and so they will know what to do