How to increase max speed of wave

[noname1]

2) The point in the middle of the string is the maximum speed, at this point occurs when the point passes through its equilibrium position (the position it occupies when the string is perfectly flat). To increase the maximum speed of this point which of the following would you change? Select all that apply.

a)Increase the amplitude
b)Decrease the amplitude
c)Increase the frequency
d)Decrease the frequency
e)Increase the string thickness
f)Decrease the string thickness

i would think its a,c and f but it is incorrect can anyone help me understand why

 

[Raskolnikov]

I believe we would want (e) and not (f). A thicker string would result in a greater affinity for the string to return back to its equilibrium position. Think of it as: It takes more effort to pull a thicker string, so it'll have a 'stronger desire' to return back to its original position.