If the students continued moving the ends of the rope up and down the same distance (which means the amplitude stays the same) but moved the ends faster, the waves produced would have a higher frequency because they are creating more wave cycles in a given amount of time. According to the wave relationship, if the frequency increases and the amplitude remains constant, the wavelength, which is the distance between consecutive wave peaks, would decrease.
Therefore, the correct response would be:
The frequency would increase and the wavelength would decrease, but the amplitude would be unchanged.