I believe that the answer is C<span />
Answer:
Sound needs a material medium for their propagation like solid, liquid or gas to travel because the molecules of solid, liquid and gases carry sound waves from one point to another. Sound cannot progress through the vacuum because the vacuum has no molecules which can vibrate and carry the sound waves.
True since coulomb's law states that There is electric force between like charges or opposite charges. The negative sign only shows the nature of the force.
<h3>What is the coulombs law ?</h3>
coulombs formula is given by

Now it states that if two charged particles are separated by the distance r and having same or opposite charge will attract or repel each other.
The intensity of the force depend upon the distance and the nature of the charge.
Hence coulomb's law states that There is electric force between like charges or opposite charges. The negative sign only shows the nature of the force.
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Answer: 
Explanation:
A direct proportionality means a linear relationship between two variables and rate of change means an application of derivatives. Hence, the mathematical model is:
