Headache
exhausted
less
patrick

Step-by-step explanation:

c is correct.  To verify this, look at the point (4, 4) on the black graph.  For the same x value (4), we have on the red graph the point (4, 2).  If we now look at this point (4, 2) on the red graph we see that the y-value (2) is half that of the point (4, -4) on the black graph:  f(x) = (1/2)y