Rightward Supply Shift Boosts Consumer Surplus Steps:

• Define consumer surplus as the difference between consumers' willingness to pay (demand curve) and the actual market price, up to equilibrium quantity.
• Identify equilibrium as intersection of demand and supply curves under normal conditions (downward-sloping demand, upward-sloping supply).
• Analyze supply shift right: increases supply at each price, moving equilibrium to lower price and higher quantity.
• Conclude effect: lower price expands surplus per unit; higher quantity adds more surplus area.

Why D is correct:

• A rightward supply shift lowers equilibrium price and raises quantity, expanding the consumer surplus triangle under the demand curve per standard microeconomic surplus calculation.

Why the others are wrong:

• A: Leftward demand shift reduces willingness to pay, lowering quantity and shrinking surplus area.
• B: Leftward supply shift raises price and lowers quantity, contracting surplus by increasing cost per unit.
• C: Rightward demand shift raises price despite higher quantity, reducing surplus per unit and not definitely increasing total surplus.

Final answer: D