Which two (2) types of data can be displayed by default in the Application Overview...

The Application Overview dashboard in QRadar includes various default items1. Two of these items are Top Applications (Total Bytes) and Outbound Traffic by Country (Total Bytes)1.

Default dashboards - IBM Documentation

According to the IBM Security QRadar SIEM V7.5 documentation, the Application Overview dashboard by default includes items such as "Inbound Traffic by Country (Total Bytes)," "Outbound Traffic by Country (Total Bytes)," and "Top Applications (Total Bytes)" among others. This confirms that options C and D are displayed by default on the Application Overview dashboard​​.