Question

18. Which of the following would lower the pitch of a string instrument's sound?

A. increasing the thickness of the string used.

B. using less force to vibrate the string.

C. adding tension within the string.

D. shortening the effective string length.

Please provide an explanation. Don't answer unless you're 100% sure. Thanks!

Answer 1

It would be A. increasing the thickness of the string used. 
A thicker string will vibrate slower, making the pitch lower. 

Answer 2

your answer is increasing the thickness of the string used.

i just took the test