The electromagnetic waves with the most energy have the greatest period
b) wavelength
c)
frequency
d) color

Frequency is the amount of times the particle moves back and forth per second, more or less. The more energy, the higher the frequency. At the same time, the more energy means you'll have a shorter wavelength (aka period). Color only applies to the visible spectrum.

frequency

Explanation: The greater the number of waves appear the greater the energy. The smaller the number of waves appear the lower the energy.

Frequency is the number of times waves appear.

c the car's velocity increases constantly over time.