Question

Which term describes the number of crests that pass a point in a given amount of time?

Answer 1

I don't know what you mean by crests, but im pretty sure the answer you are looking for is C. Frequency. Just look at frequency in general, it means the amount of times an object does in a certain amount of time. Now compare to my answer, doesn't it look similar? Hope this helps!

Answer 2

I believe this would be frequency, as wavelength measures the waves themselves, and a period is a section of time. Wave speed is the speed of their movement.