Final answer:
The correct statement about substitutes is that consumers generally are willing to pay more for a product with no close substitutes, indicating the product's uniqueness and lack of alternatives.
Step-by-step explanation:
The true statement about substitutes is that you are usually willing to pay more for a product with no close substitutes. This reflects the idea that when a product has no close substitutes, consumers see that product as unique and may be willing to pay a premium for it since they cannot easily replace it with an alternative. If a product truly has no substitutes, this may create a situation where a firm could be considered a monopoly if it is the only producer of that product. However, when there are similar options available, the firm would not hold a monopoly. The concept of opportunity cost is related to the choices consumers make when they forgo one product for another, while rational consumer behavior is based on the idea that they seek to maximize utility, comparing the marginal utility of a good with its opportunity cost.