Strontium. Hope that helps
Answer:
(a) 
(b) 
Explanation:
The angular speed is a measure of the rotation speed. Thus, It is defined as the angle rotated by a unit of time:

The arc length in a circle is given by:

s is the length of an arc of the circle, so
.
Replacing (2) in (1):

a) Now, we calculate the angular speed:

b) We use (1) to calculate the time it takes to make one revolution, which means that
is
.

A. nucleus
hope this helps if so please mark me brianliest
<span>Refraction is where the direction of travel of sound waves is altered by passing through a material of much higher or lower density. Walls that allow sound through are one example, but answer B is more about walls bouncing sound back - that's an example of reflection. The most likely change of density is answer A, air with big temperature differences.</span>