Explanation:
the other answer was already right.
yes, C (-3, -3) and (-3, 3)
but why ?
the slope is the y/x ratio of the x and y coordinate differences when going from one point to the other.
so, x changes 0 units. y changes 6 units (from -3 to 3).
so, the slope is 6/0 = infinite or simply undefined.
this is a vertical line at x = -3.