Final answer:
The statement that substitute products include those offered by close competitors is true. Substitute availability affects market competition and can lead to a shift in demand curves when consumers opt for alternatives due to changes in pricing or availability.
Step-by-step explanation:
Substitute products do indeed include those offered by close competitors. This statement is true. When a firm produces a product that lacks close substitutes, it can be considered a monopoly producer within a particular market.
However, the presence of similar products, even if not identical, from other firms means that consumers have choices, and thus, the firm is not in a monopolistic position.
The degree to which alternatives are considered close substitutes can be a subject of debate, as the substitute availability affects the elasticity of demand for a product.
For instance, as the price of tablet computers falls, making them more accessible, there may be a decrease in demand for laptops, considered a substitute, resulting in a leftward shift in the demand curve for laptops.