Answer:
C
Step-by-step explanation:
The period of a sine function can be found by looking at the argument.
In the equation y = Sin (ax), ax is the argument, and period is 360/a.
For the function shown, y = Sin x, the period is 360/1 = 360. This means that the period is the number of months it takes to complete one cycle of the graph (take one point in the graph and run along the curve until the same point is reached).
If we take January as the first point (y = 40) and run along until i come to same point, we are back to next years' January. Hence, the period is 12 months. Answer choice C is right.
