What clause allows the use of an alias in the WHERE statement for an expression?

The correct choice is based on the functionality of the "calculated" keyword in SAS. The "calculated" clause allows you to refer to a computed value (an alias) created in the SELECT statement within the WHERE clause of a PROC SQL query. This means that if you create an alias for an expression using the SELECT statement, you can use "WHERE calculated" followed by the alias name to filter results based on that computed value.

For instance, if you have a variable or expression defined in your SELECT that you want to apply a condition to in your WHERE clause, using the "calculated" clause lets SAS know you're referencing that newly created alias rather than the underlying data source directly. This capability is particularly beneficial in complex queries where multiple calculations or derived values are involved.

The other selections do not correspond to valid clauses for using an alias in the WHERE statement in SAS. Understanding this difference emphasizes the power of the "calculated" keyword in facilitating specific data filtering based on prior computations.