tolong jwb,beserta jalanya

2 ½ λ = 20 m
5/2 λ = 20 m
λ = 20 × 2/5 = 4 × 2
λ = 8 m

f = n/t
f = (5/2) / 5
f = 2,5/5 = 25/50
f = 1/2 Hz

Opsi : [A]