For her birthday, amy received flowers that had a dull red appearance. compared with the entire range of visible light waves, the flowers reflected relatively frequency and amplitude light waves.

The flowers reflect relatively low frequency and low amplitude light waves.
White light contains a spectrum of colors, and red light is at the beginning of this spectrum in terms of energy. This means that it has the lowest frequency, as the energy of a wave of light is directly proportional to its frequency.
The amplitude of a light wave gives a measure of how intense the light is. A dull light means that the amplitude of the wave is low.