The speed will increase four (4) times when the frequency of sound wave is increased four (4) times.
<h3>How to calculate the
frequency of a
wave.</h3>
Mathematically, the frequency of a sound wave is given by this formula:

<u>Where:</u>
- F is the frequency of a sound wave.
- V is the velocity of a sound wave.
is the wavelength of a sound wave.
<u>Note:</u> The frequency of the sound wave is increased four (4) times.
Substituting the given parameters into the formula, we have;

Therefore, the speed will increase four (4) times when the frequency of sound wave is increased four (4) times.
Read more on sound wave here: brainly.com/question/19250621
Answer:
(a) Moon has smaller diameter and lower density than earth
Explanation:
Moon has smaller diameter than earth earth has a diameter of 12742 km whereas moon has a diameter of 3474.21 km
So for density density is given by 
From the relation we can see that density is dependent on mass and volume directly proportional to mass and inversely proportional to diameter
But in case of earth and moon mass is more dominating than volume so density is less for moon than earth
The answer is C) Solar eclipse.
Hope this helps!