Lowest center of mass minimizes height from base

Steps:

• Center of mass (CM) of uniform block is at geometric center, so height equals half the vertical dimension.
• Face Y is larger than face X, so placing on Y makes vertical height smaller than on X.
• Heavy weight on top shifts overall CM upward, as combined CM formula weights masses by positions.
• Lowest CM occurs with smallest height and no added mass above.

Why B is correct:

• Positions block on larger face Y, minimizing vertical height; CM height is half that per uniform density definition.

Why the others are wrong:

• A: Smaller face X increases vertical height, raising CM.
• C: Face X maximizes height, and top weight shifts CM higher via $\bar{y} = \frac{m_1 y_1 + m_2 y_2}{m_1 + m_2}$.

Final answer: B