Correct Option: C

On comparing the given equation
E (z, t) = 10 cos (2π × 10⁷ t – 0.1 πz) with standard equation
E (z, t)=E₀ cos (ωt – βz)
ω = 2π × 10⁷, β = 0.1π

velocity, v =	ω	=	2 π × 107	= 2 × 108m/s
	β		0.1 π