You connected to the database using the following connection string： CONNECT hr/hr@test.us.oracle.com：1521/mydb  Which three statements are correct regarding the connection string？（）

• A、mydb is a service name.
• B、test.us.oracle.com is a database name.
• C、1521 is the listener port number.
• D、mydb is a host name.
• E、test.us.oracle.com is a net service name.
• F、hr is a username.
• G、test.us.oracle.com is an instance name.