Final answer:
Slicing a rectangular pyramid parallel to its base yields a smaller rectangle, because the cross-section is similar to the shape of the base but scaled down.
Step-by-step explanation:
When a two-dimensional figure is obtained by slicing a three-dimensional object, the resulting shape is dependent on the orientation of the slice relative to the object. In this case, a rectangular pyramid is being sliced parallel to its base. The base of a rectangular pyramid is a rectangle, and when cut parallel to this rectangle, the resulting cross-section will be similar in shape to the base but scaled based on the location of the slice within the pyramid.
If the slice is parallel and completely through the pyramid, you will get a smaller rectangle. If the pyramid is truncated by the slice, it creates two additional parallel sides, making another rectangle. This logic concludes that the correct answer is:
A. rectangle