Final answer:
The coordinates of C after reflecting the parallelogram across the y-axis are (2, 2).
Step-by-step explanation:
When a figure is reflected across the y-axis, the x-coordinates of all its points are negated. To find the coordinates of C after reflecting parallelogram ABCD across the y-axis, we negate the x-coordinate of point C.
So, the coordinates of C after reflection are (2, 2).