For this polygons , all the reflections that carry the figures onto themselves are :
A. Reflect the rectangle across a line through the midpoint of opposite sides.
B. Reflect the parallelogram across a line that passes through the opposite vertices.
C. Reflect the regular heptagon across a line that passes through the center of the heptagon.
The only reflections that will carry the figures onto themselves are those that reflect across a line that passes through the center of the figure. In the case of the rectangle, this would be the line that passes through the midpoint of opposite sides. In the case of the parallelogram, this would be the line that passes through the opposite vertices. And in the case of the heptagon, this would be the line that passes through the center of the heptagon.
So the answer is:
A. Reflect the rectangle across a line through the midpoint of opposite sides.
B. Reflect the parallelogram across a line that passes through the opposite vertices.
C. Reflect the regular heptagon across a line that passes through the center of the heptagon.