Supply Decrease from Regulations

Steps:

• Identify the change: assumes a decrease in fresh fish supply, as D limits quantity caught.
• Recall supply shifters: non-price factors like regulations, costs, or technology affect supply curve.
• Evaluate options: select factor causing leftward supply shift (reduced quantity at each price).
• Confirm D: restrictions directly lower available fish, decreasing supply.

Why D is correct:

• Regulations act as a supply shifter by imposing quotas, reducing quantity supplied at every price (per supply curve definition).

Why the others are wrong:

• A: Favorable weather boosts catches, increasing supply (rightward shift).
• B: Substitute popularity lowers demand, not supply; price fall is an effect, not cause.
• C: Health promotions raise demand, shifting demand curve rightward, not supply.

Final answer: D