Answer:
(A) Tightening and loosening strings change the pitch because of tension. The tension gives the string the ability to create waves.
(B) The strings of lower tones are thicker because the heavier the string the slower the waves. The slower the waves the deeper the frequency is. Same with tightening and loosening the string. The waves move slower and are smaller because the weight of the string affects its movement.
(C) When you place your fingers on the strings the pitch is heightened because you are shortening the length of the string and creating more tension.
Explanation:
(A) The tighter the string, the closer the waves are to each other because there is less room to move. The looser the string, the further and smaller the waves will be, causing the tone to become lower.
(B) It's like dropping a basketball onto a court. If you fill that basketball with oxygen it will have a higher pitch when dropped than a basketball full of cement or beans.
(C) The higher on the neck of the instrument you go the higher the pitch goes because you are shortening the wave distance.
(Sorry for the long explanation, good luck)
