Which two of the following are true about session variables and repository variables?

A.
Sessions variables are created and assigned a value when a user logs in

B.
sessions variables can be used in queries but repository variable cannot

C.
repository variables have a single value for all users at any point in time

D.
repository variable cannot be modified except by restating the server

E.
BI server substitutes the values of the session variable for the variable contained in the analytics repository