Question

the note a4 (the a above middle c on the piano) sounds at a vibration of ...
○ 440hz
○ 380hz
○ 220hz

question 9
what is hertz (hz) in music?
○ a rental car company
○ how many times something happens in 1 second
○ pain

Explanation:

First Question (About A4 note frequency)

In music, the standard tuning for A4 (A above middle C) is 440 Hz. 380 Hz and 220 Hz do not match the standard frequency for A4.

Question 9 (What is hertz (Hz) in music?)

Hertz (Hz) is a unit of frequency, defined as the number of occurrences (like vibrations of a sound wave) per second. A rental car company (Hertz the company) is unrelated, and "pain" has no relation to the unit Hz in music.

Answer:

A. 440 Hz