Answer:
c. wavelength
Explanation:
The speed of the wave on the string is given by
Here, \mu is the mass per unit length and T is the tension in the string.
For the different thickness, the mass per unit length is different. Therefore, the wave speed is different in the two strings.
The frequency of the oscillations depends upon the oscillator. So, the frequency is same for the two strings by using same oscillator.
The frequency and speed relation is,
f= γλ
λ= f/γ
Since frequency is constant, the wavelength of the waves different as the speeds are different.