Which function describes the graph in the picture? need asap

-- The function is a sine or cosine that wiggles from 3 below to 3 above its average value.  So the amplitude is 3 .  That lets out the 1st and 3rd choices.
It has to be the 2nd or 4th choice.

Looking at the graph, the y-intercept is at  y=6.
The y-intercept is the point where x=0,  so f(0)=6.

Test the 2nd choice:    f(x)  =  3 cos(x)  +  3

                                 f(0)  =  3 cos(0)  +  3

cos(0) = 1   so           f(0)  =  3 (1)       +  3          = 6

Choice-2 is looking good. 
Just to be sure, let's check choice-4:

                                 f(x)  =  3 sin(x)  +  3

                                 f(0)  =  3 sin(0)  +  3

sin(0) = 0       so        f(0)  =  3 (0)       +  3      = 3

Beautiful !  Choice-4 flopped.  The answer is choice-2 .