Which two statements are true regarding subqueries? (Choose two.)
Only two subqueries can be placed at one level.
A subquery can be used to access data from one or more tables or views.
If the subquery returns 0 rows, then the value returned by the subquery expression is NULL.
The columns in a subquery must always be qualified with the name or alias of the table used.
A subquery in the WHERE clause of a SELECT statement can be nested up to three levels only.