Concept:A bureau-de-change is a financial service outlet that deals mainly in the exchange of one national currency for another.
Explanation:The core activity is the buying and selling of foreign currency.
It buys foreign money from travellers or businesses and sells foreign money to customers who need it.
Its profit comes from the difference between the buying rate and the selling rate.
It does not mainly trade securities, general trade information, or physical goods and services.
Therefore, the primary function matches option A.
Answer:A. buying and selling foreign currency