Which function describes the graph shown below?

On a coordinate plane, a curve crosses the y-axis at (0, negative 2), increases to negative 2.5, decreases to negative 2.5, and then increases again.
y = one-half sine (x) minus 2
y = 2 sine (x) minus one-half
y = one-half cosine (x) minus 2
y = 2 cosine (x) minus one-half