Frequency is: A. the noise floor acceptable in recording
B. the distance between the top or bottom of a wave and the center of the wave
C. the distance between two identical points on a wave
D. the number of waves in a certain amount of time

this is actually for music but there's no music topic so..

I think it is (D)

Explanation:

Because in our definition . Frequency is the number of vibrations of an object per second and it sounds the same with answer (D)

d) she is both terrified and excited by the idea of returning to school.

a) she takes one day at a time.

d) she felt like she was an object of ridicule.

d) she tells her daughter not to worry about it because things will get better.\

b) elnora needs money for books and out-of-town tuition. she will raise the money herself.

the author develops a cold, and scared tone. making the reader shudder with fear, and suddenly become cold. i'm guessing that he's writing a scary novel, or maybe about a chilly december night.