Please check my answer!! I would be great if you could explain this to me a little as well...

To find the amplitude, measure_____

a. the horizontal distance between consecutive positions
b. the horizontal distance between a consecutive crest and trough
c. vertical distance from crest to trough
b. vertical distance from a crest to a rest position**

I think its the last one but this question is a little confusing.

2 answers

D. you are correct.
agree
y = A sin (2 pi f t)
so A is half the distance from sin = -1 to sin = +1
or from sin = 0 to sin = 1