The correct answer for the question that is being presented above is this one: "B. 13m."
The formula of wave velocity is this:
wave velocity = f * λ
λ = v / f
λ = 343m/s / 26Hz
λ = 13.20m .. ans (b)
Here are the following choices:
A. 5m
B. 13m
C. 28m
D. 58m