Step 1: The hexagonal prism (P) when cut can reveal various polygonal cross-sections, including hexagonal and rectangular sections. However, a square cross-section is not possible with this object unless cut in a very specific direction.
Step 2: The cube (Q) can easily reveal square cross-sections as it's a regular 3D object. It can also produce rectangular and other polygonal sections.
Step 3: The cylinder (R), due to its circular symmetry, can reveal curvilinear sections if cut at an angle to its axis. It can also reveal square cross-sections when cut perpendicular to its axis. Hence, both P and R can reveal square cross-sections under certain orientations of the cutting plane.
Step 4: After evaluating all possibilities, we conclude that the correct answers are (A), (B), and (C).