Answer:
The wave diagramed in blue.
Step-by-step explanation:
The reason for this is because frequency is explained as the number of times something has occurred in a certain period of time.
Here, we are talking about wavelength, so the frequency is the number of times the wave can oscillate in this time length.
Say we make dots on the middle of each downward slope. How long does it take to get to each dot compared to the other diagram? The answer is the one with the least amount of time. The wave diagramed in blue.