Question

how do we measure the amplitude of a wave?
from the resting position to top or resting position to bottom
from the starting point to ending point of a wave
from top to bottom
from top to top or bottom to bottom

Explanation:

The amplitude of a wave is the maximum displacement of a particle from its resting position. So, it is measured from the resting position to the top (crest) or from the resting position to the bottom (trough) of the wave.

Answer:

from the resting position to top or resting position to bottom