If a number of sine waves with modulation indices `n_(1),n_(2),n_(3)`… modulate a carrier wave, then total modulation index (n) of the wave is
A. `n_(1) + n_(2) ....... + 2(n_(1) + n_(2).......)`
B. `sqrt(n_(1) - n_(2) + n_(3)......)`
C. `sqrt(n_(1)^(2) + n_(2)^(2) + n_(3)^(2)......)`
D. None of these