Why do you use APIs?

SAP S / 4HANA Cloud Configuration and Integration

Why do you use APIs? Note: There are 2 correct answers to this question.
A . To enhance pre-delivered applications with custom fields for your SAP S / 4HANA Cloud system
B. To create a data definition for extending a CDS view in your SAP S / 4HANA Cloud system
C. To integrate apps inyour SAP SAP S / 4HANA Cloud System with SAP Cloud Platform
D. To connect your SAP S / 4HANA Cloud system to other systems

Answer: C,D