You work in a company which uses SQL Server 2008. You are the administrator of the company database. Now you are in charge of a SQL Server 2008 instance on the same physical computer. Now users report that they are unable to connect to the named instances. You check and verify that they can only connect to the default instance. You also ensure that all SQL Server instances run normally. You have to start the service which is required to connect to the named instances. Which service should you start?（）

A. Server
B. SQL Server Agent
C. SQL Server Browser
D. SQL Active Directory Helper