Which equation shows right ratio between the frequency （f) and the wavelength （Lambda) of

Which equation shows right ratio between the frequency (f) and the wavelength (Lambda) of radio waves？

A.f=Lambda/C

B.f=C x Lambda

C.f=C/Lambda

D.f=C x 6.28 x Lambda

请帮忙给出正确答案和分析，谢谢！