ANSWER
D. Both b and c are correct
EXPLANATION
In the equation
[tex]f=\frac{c}{\lambda}[/tex]f is the frequency of the wave, c is the speed of light - which is 3 x 10⁸ m/s, and λ is the wavelength. For this wave, the frequency is
[tex]f=\frac{3\cdot10^8m/s}{50m}=6\cdot10^6hz[/tex]Therefore option B is correct. But remember that the prefix mega adds six zeros to the right of the number, so option C, 6 megahertz is correct too, since:
[tex]6\text{ megahertz}=6,000,000\text{ hertz}=6\times10^6\text{ hertz}[/tex]Hence, the answer is D. both B and C are correct.
