Which two report formats can be used as a source report to configure a reporting...

For reporting snapshots, the source report must be capable of grouping data, which is necessary for summarizing information at specific intervals. The acceptable formats for a source report in reporting snapshots are:

Summary format (B). This format groups rows of data by one or more criteria and can perform calculations such as sum, average, etc., on another column at each group level.

Matrix format (D). Similar to the summary format but arranges data in a grid format, allowing summarization by both rows and columns.

Tabular (A) and joined (C) formats are not suitable for reporting snapshots. Tabular reports do not include grouped or summarized data, and joined reports involve combining multiple report types, which are not compatible with how reporting snapshots need to structure data.

Reference for more information on reporting snapshots and report formats:

Reporting Snapshots: https://help.salesforce.com/articleView?id=reports_snapshots.htm &type=5

Report Formats: https://help.salesforce.com/articleView?id=reports_understanding_formats.htm &type=5