You design a Business Intelligence (BI) solution by using SQL Server 2008. A SQL Server 2008 Reporting Services (SSRS) instance contains a report. Employees execute the report by using Report Manager.
Each employee has his own specific set of parameters to execute the report. Data for the report is updated once daily. For each employee, the report takes more than five minutes to execute. You discover that data retrieval takes most of the time during report execution. You need to reduce the execution time of the report.
What should you do?

A.
Create a report execution snapshot.

B.
Create a data-driven subscription that uses the NULL delivery method.

C.
Create a data-driven subscription that uses the file share delivery method.

D.
Create a standard subscription that uses the file share delivery method.

Explanation:
Tip: "specific set of parameters" = "NULL"

Data-Driven Subscriptions
A better name for a data-driven subscription might be mass mailing. The data-driven subscription enables us to take a report and e-mail it to a number of people on a mailing list. The mailing list can be queried from any valid Reporting Services data source.The mailing list can contain fields in addition to the recipients e-mail address, which are used to control the content of the e-mail sent to each recipient.

http://msdn.microsoft.com/en-us/library/ms159762.aspx
Standard and Data-Driven Subscriptions
Reporting Services supports two kinds of subscriptions: standard and data-driven.
Standard subscriptions are created and managed by individual users. A standard subscription consists of static values that cannot be varied during subscription processing. For each standard subscription, there is exactly one set of report presentation options, delivery options, and report parameters.
Data-driven subscriptions get subscription information at run time by querying an external data source that provides values used to specify a recipient, report parameters, or application format. You might use data-driven subscriptions if you have a very large recipient list or if you want to vary report output for each recipient. To use data-driven subscriptions, you must have expertise in building queries and an understanding of how parameters are used. Report server administrators typically create and manage these subscriptions.
Delivery Extensions
Subscriptions use delivery extensions to determine how to distribute a report and in what format. When a user creates a subscription, he or she can choose one of the available delivery extensions to determine how the report is delivered. Reporting Services includes the following delivery extensions. Developers can create additional delivery extensions to route reports to other locations.
Windows File Share – Delivers a report as a static application file to a shared folder that is accessible on the network.
E-mail – Delivers a notification or a report as an e-mail attachment or URL link.
SharePoint library – Delivers a report as a static application file to a SharePoint library that is accessible from a SharePoint site. The site must be integrated with a report server that runs in SharePoint integrated mode.
Null – The null delivery provider is a highly specialized delivery extension that is used to preload a cache with ready-to-view parameterized reports This method is not available to users in individual subscriptions. Null delivery is used by administrators in data-driven subscriptions to improve report server performance by preloading the cache.