Final answer:
The best scenario reflecting the income effect is when Ian cuts back on all purchases due to a rise in the price of clothes, indicating that his buying power has decreased.
Step-by-step explanation:
The scenario that best reflects the income effect is A. Ian responds to a rise in the price of clothes by cutting back on all of his purchases. This reflects the income effect because an increase in the price of clothes reduces Ian's effective buying power, meaning that, even though his actual income hasn't changed, he feels as though he has less money to spend on all types of goods.
The income effect occurs when a change in the price of a good affects the consumer's ability to purchase other goods with the same income. Conversely, the substitution effect occurs when consumers replace a more expensive good with a less costly alternative, which is not the scenario described by Ian's reaction.