Which of the following could be the equation of the function below?

Option C is the correct option.

Step-by-step explanation:

In the given cosine graph we can draw some parameters of the equation as below

y = a cos(bx + c) + d

1) amplitude a = (1+3)/2=2

2) Period = π

3) phase shift = -π ( to the left)

4) Vertical shift = -1 ( downwards on y-axis)

Therefore the equation of the graph will be

y = -2cos[2(x + π)] - 1

Option C is the correct answer.