Demand Curve Shift from Non-Price Factors

Steps:

• Identify that demand curve shifts from changes in non-price determinants like income, tastes, prices of related goods, or expectations.
• For public transport, D2 likely shows a leftward shift (decrease in demand) based on the options.
• Evaluate each choice: price changes cause movement along the curve, while quality affects tastes/preferences.
• Select the option that decreases willingness to buy public transport at every price.

Why D is correct:

• A decline in quality reduces consumer preferences for the good, shifting the demand curve left per the law of demand (non-price factor alters quantity demanded at each price).

Why the others are wrong:

• A: Eliminating car costs makes cars cheaper (substitute effect), shifting demand left—but "banned" phrasing is unclear; still, not the direct cause specified.
• B: Being banned from driving removes the substitute, increasing demand and shifting the curve right.
• C: A price rise causes movement up along D1, not a shift to D2.

Final answer: D