Answer:
c. increase in the demand for muffins.
Step-by-step explanation:
Substitutes means that the product can be used to replace the others. If muffins and bagels are substitutes, then consumer who wants to eat muffin can choose bagel instead, and vice versa.
If the price of bagels keep increases, it will make the muffin seems relatively cheaper than bagels. People will start to buy some muffin instead of bagels. This will result in an increase of the muffin demand.
