The correct answers are:
A, C and D.
Explanation:
The height of a parallelogram must be perpendicular to, or make a right angle with, the base of the parallelogram.
In parallelogram A, it is a rectangle; this means by definition the side is at a right angle with the base and is therefore a height.
In parallelogram B, the short side is marked as the height. However, this side is not at a right angle with the base, so it cannot be a height.
In parallelogram C, the height is drawn perpendicular from the vertex of the top base to the (extended) bottom base; this is correct, since it is at a right angle.
The same is true of parallelogram D.
