The correct answer is 4. Stimulus.
Explanation
A stimulus is a term used to refer to the impact or influence that an action has on a system. For example, in the case of living beings, the stimulus is that which causes response or reaction from the body. This term is also used in the economic area to refer to an action that causes consumers to purchase a good or service, generally, the stimuli are discounts, promotions, consumer benefits, among others, that make the consumer consider that acquiring that service is either at a reasonable price and that it is going to allow you a greater benefit than what you would normally receive. For example, a stimulus can be the end of season discounts, which allow the buyer to be motivated to buy more products for a small discount.