Answer:
Answer is B (assuming it's meant to say 4.3 x 10^10 Hz)
Explanation:
Right away you can eliminate A and C because the units are wrong - m/s is units of speed, not frequency (whose units are Hz).
In general the product of an electromagnetic wave's wavelength (λ) and frequency (f) in a vacuum is equal to the speed of light (c):
λf = c
Knowing that c = 3 x 10^8 and λ = 0.07 you get:
0.07f = 3 x 10^8
f = 3 x 10^8 / 0.07
f = 4.3 x 10^10
