Which of the following statements regarding BAPIs are correct?

Business APIs (BAPIs) can be used to trigger and execute transactions in an SAP landscape.

Which of the following statements regarding BAPIs are correct? There are 2 correct answers to this question.
A . Data exchange by BAPI can only be done by asynchronous RFC
B . BAPI communication requires a connection to a central LDAP directory server
C . BAPIs are specialized remote function calls
D . BAPIs can be used for connecting external software to SAP systems

Answer: C,D