You have a SharePoint site collection that contains 100 sites. Each site contains 100 lists.

You need to retrieve the data from all of the lists. The data must be retrieved in the minimum amount of time.

Which access method should you use?

A.
ListData.svc

B.
SPListItemCollection.GetDataTable

C.
SPList.Items

D.
SPSiteDataQuery

Explanation:
MNEMONIC RULE: “100 sites = SPSite”

The data must be retrieved in the minimum amount of time; therefore, SPSiteDataQuery

SPSiteDataQuery Class
http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.spsitedataquery.aspx