Which of the following can shift the demand curve to the left?

The correct choice, a decline in consumer preferences, effectively illustrates how demand can decrease for a product or service. When consumer preferences shift away from a particular good, it indicates that consumers are less inclined to purchase it, even at existing prices. This reduction in desirability prompts a leftward shift in the demand curve, reflecting lower demand at all price levels.

In contrast, an increase in consumer income generally results in a rightward shift of the demand curve for normal goods, as consumers possess more purchasing power. A decrease in the price of substitutes usually increases the demand for the substitute goods, which, depending on the good in question, can also shift its demand curve to the left. Anticipated future price increases can lead to a rightward shift, as consumers may choose to buy more in the present rather than wait for higher prices. Thus, understanding shifts in demand requires a clear grasp of how preferences and related factors interact within the market.