This is Physics and EP should answer this one! But here is my two-cents' worth.
When you approach a source of stationary light, or the other way around, when the source of light is moving towards you, its frequency shifts to the blue end of the spectrum. But, the frequency of blue light is not a constant number but ranges between ~6.1 - 6.7 x 10^14 Hz. Since the choices given are so close to each other, I would say that whatever they measure is the frequency of the light source, 4.39 x 10^14 Hz.
Note: Some expert should check this.
