(A) : Heavy boxes are loaded along with empty boxes on a cart. Heavy boxes should be kept at the centre of gravity of the cart, for more stability.

(R) : The vertical line passing through the centre of gravity should fall within the base of cart for stability.

• To keep the CG of the loaded cart low, the heaviest boxes should be loaded first. This guarantees equilibrium stability.
• The weight acts at CG in a vertical line.
• The line (vertical) through CG must lie in the base (area of support for stability.

Hence the correct answer is Both 'A' and 'R' are true and 'R'  is the correct explanation of 'A'.