Your network contains a Windows Server Update Services (WSUS) server named Server1. You discover that certain updates listed in the WSUS administrative console are unavailable on Server1. You need to ensure that all of the updates listed in the WSUS administrative console are available on Server1. What should you do on Server1?

A.
Restart the Update Services service.

B.
Run wsusutil.exe and specify the reset parameter.

C.
Run wsusutil.exe and specify the deleteunneededrevisions parameter.

D.
Run wuauclt.exe and specify the /detectnow parameter.

Explanation:

reset :Checks that every update metadata row in the database has corresponding update files stored in the file system. If update files are missing or have been corrupted, WSUS downloads the update files again.
use it :
After restoring the WSUS database.
When troubleshooting
http://technet.microsoft.com/en-us/library/cc720466%28WS.10%29.aspx