Answer:
D. Parallel to the base
Explanation:
We are given that,
A cross-sectional slice created the rectangular cross-section on the cake.
It is required to find the the cross-section.
From the figure, we see that,
The rectangular cross-section can be obtained only when the cake is cut horizontally.
That is, the cross-sectional slice is parallel to the base.
So, option D is correct.