The correct answer is:
A) pyramid
Step-by-step explanation:
When you take the cross-section of a pyramid parallel to the base, the cross-section will be in the shape of the base.
As you take cross-sections further up the pyramid, you will still get a cross-section that is in the shape of the base, but it will be smaller. This is because as you go further up the pyramid, the distance between vertices is shorter because it comes to a point.