You work in a company which uses SQL Server 2008. You are the administrator of the company database. In your company there is a server which contains a default SQL Server 2005 instance. For a new application, you have to install a SQL Server 2008 instance on the server. Your company CIO assigns a task to you. You must make sure that the respective certified third-party applications have access to both database instances. You have to achieve this goal without changing the existing application environments. So what should you do to achieve this by using as little database administrative effort as possible?（）

A. You should install SQL Server 2008 as a named instance, and make the new application to use the new instance.
B. You should install SQL Server 2008 as the default instance, and make the new application to use the default instance.
C. You should upgrade the SQL Server 2005 application to use SQL Server 2008.
D. You should upgrade the SQL Server 2005 instance to a SQL Server 2008 instance.&e