A student examines a displacement–versus–position graph of a water wave at one instant. Consecutive crests occur at positions 0.00 m, 0.20 m, 0.40 m, and 0.60 m along the positive x-axis. Which of the following is the wavelength of the wave?
(a) 0.40 m
(b) 0.20 m
(c) 0.60 m
(d) 0.15 m