If microwaves, X rays, infrared, gamma rays, ultra-violet, radio waves and visible parts of the electromagnetic spectrum are denoted by M, X, I, G, U, R and V then which of the following is the arrangement in ascending order of wavelength ?
a. R, M, I, V, U, X and G
b. M, R, V, X, U, G and I
c. G, X, U, V, I, M and R
d. I, M, R, U, V, X and G