Which Transact-SQL statement should you use?

You are migrating a database named Orders to a new server that runs Microsoft SQL Server 2012.

You attempt to add the [CorpnetUser1] login to the database.

However, you receive the following error message:

"User already exists in current database."

You need to configure the [CorpnetUser1] login to be able to access the Orders database and retain the original permissions. You need to achieve this goal by using the minimum required permissions.

Which Transact-SQL statement should you use?
A . DROP USER [User1];
CREATE USER [CorpnetUser1] FOR LOGIN [CorpnetUser1];
ALTER ROLE [db_owner] ADD MEM3ER [CorpnetUser1];
B . ALTER SERVER RCLS Isysadmin] ADD MEMBER [CorpnetUser1];
C . ALTER USER [CorpnetUser1] WITH LOGIN [CorpnetUser1];
D . ALTER ROLE [db owner] ADD MEMBBR [CorpnetUser1];