※This sample exam is different from those that appear in the actual OSS-DB Exam.
current_user is a function that returns the name of the user executing the context and takes no arguments.
There is no user change function as described in C or D.
It is a function that occupies a special position in SQL and parentheses can not be added after the function name. It will result in an error. In the same way, there are current_date and so on as a function that gives an error when you put parentheses.
Therefore, the correct answers are B and E.