What defines cross-border payments?

Cross-border payments are characterized by transactions that occur between parties located in different countries. This entails the transfer of funds across national borders, often involving different currencies, regulations, and banking systems. The correct answer accurately reflects this definition by specifically identifying ACH (Automated Clearing House) payments, which can indeed occur between accounts located in different countries.

In the context of cross-border payments, it's important to note how they differ from domestic transactions. While options that refer to payments within a single country or those exchanged in the same currency do not fit, the essence of cross-border payments lies in the international aspect of the transaction. Payments processed through traditional banking channels may include both domestic and cross-border transactions, making it a broader term that does not specifically define the nature of cross-border payments. Thus, option B is the only one that captures the critical element of cross-border transactions, which is the international exchange of funds.