Demand Curve Shifts vs. Movements Steps:

• Recall that the demand curve shows quantity demanded at different prices; shifts occur due to non-price determinants like income or related goods' prices.
• A movement along the curve happens when only the good's own price changes.
• Without the diagram, D1's direction (left or right) is unknown, making it impossible to identify the exact cause.
• Options A–C affect non-price factors (substitutes, advertising, income), potentially shifting demand; D affects price, causing movement.

Why D is incorrect:

• A decrease in good G's price causes a movement down along the existing demand curve, not a shift to a new curve like D1 (law of demand).

Why the others are wrong:

• A: Could shift demand left if D1 is leftward, but direction unknown.
• B: Reduces demand, potentially left shift, but depends on D1.
• C: Increases demand for normal good, potentially right shift, but depends on D1.

Not enough information. Final answer: Not enough information.