Which of the following restrictions and options apply?

You want to use Data Source Extensions.

Which of the following restrictions and options apply? There are 2 correct answers to this question.
A . You can only create one Data Source Extension per data source.
B . You can use Data Source Extensions to extend SAP data sources with customer-specific fields.
C . You can only create Data Source Extensions for SAP applications that have been enabled by SAP for key user extensibility.
D . You can only read fields of a Data Source Extension.

Answer: C,D