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. `n_(1)+n_(2)…..`