Which statement accurately describes the nature of merchant accounts?

Merchant accounts are primarily designed to allow businesses to process credit and debit card transactions for goods and services, which includes travel agencies. Travel agencies benefit from merchant accounts as they enable them to accept payments from clients for bookings and services provided. This functionality is crucial in the travel industry where card transactions are a common method of payment for both domestic and international travel arrangements.

The other options misrepresent the purpose and usage of merchant accounts. They are not exclusively limited to large businesses since small and medium-sized businesses, including travel agencies, also utilize them. Merchant accounts are not primarily for personal transactions, which are typically handled through personal banking accounts, and they do not link to investment accounts, as these serve a different financial function altogether. Thus, stating that they can be used by travel agencies accurately reflects their role in facilitating payment processing in the travel sector.