Final answer:
Complements are goods used together where the use of one increases the use of the other. The correct answer is B) The use of one increases the use of the other, as seen with products like mobile phones and their accessories.
Step-by-step explanation:
When it comes to complements, this refers to goods that are often used together so that consumption of one good tends to enhance consumption of the other. Ceteris paribus, meaning other things being equal, if one of the complements' use increases, it will result in the increase in use of the other complement as well. Therefore, the correct answer to the student's question is B) The use of one increases the use of the other. For instance, if more people buy mobile phones, the demand for phone accessories like chargers and cases, which are complements, also tends to increase.