Answer:
Part a. A square
Part b. A square
Explanation:
A cube is a box that has six identical square faces. Hence if you take the cross-section by cutting the cube horizontally, that is, cutting it parallel to the base, the result is a square. Moreover, if you cut the cube vertically, cutting it parallel to the lateral face, the result is also a square. Finally, in both cases the cross-section is as shown in the figure below.