You design a SQL Server 2008 Reporting Services (SSRS) solution. The solution contains a report. The report includes information that is grouped into hierarchical levels. You need to ensure that the solution meets the following requirements:
When you click each level, the next level of information must be displayed. When you click the last level, detailed information must be displayed. When the report is exported to a Microsoft Excel spreadsheet, all the levels and all detailed information must be available in the spreadsheet.
Which feature should the report use?

A.
filter

B.
drilldown

C.
drillthrough

D.
a document map

Explanation:
Tip: "hierarchical levels … spreadsheet" = "drilldown"

http://technet.microsoft.com/en-us/library/dd207141.aspx
Drillthrough, Drilldown, Subreports, and Nested Data Regions (Report Builder 3.0 and SSRS)

You can organize data in a variety of ways to show the relationship of the general to the detailed.
You can put all the data in the report, but set it to be hidden until a user clicks to reveal details; this is a drilldown action. You can display the data in a data region, such as a table or chart, which is nested inside another data region, such as a table or matrix. You can display the data in a subreport that is completely contained within a main report.
Or, you can put the detail data in drillthrough reports, separate reports that are displayed when a user clicks a link.