Idk if you need it but here are my answers for part C and D (the questions after this one on plato)
C: To model this function I would choose cosine because it's graph fits better with the cycle of the moon. It would start at the highest low tide, when the moon is new, and then the graph would go down steadily back to a full moon, where the lowest low tide is when when the moon is full (strongest gravitational pull).
D: The amplitude of the function would have to be around 1.3 because the function is like a line of best fit, and it would have to be close to the points (4, 1.8) and (11, -1.4), but not include them since they are in a way maximums and minimums and the graph has to fit along with the low and high low tides of the other days.