To solve this question, the user needs to know the basic functionalities of SQL*Plus.
The feature that can be used to replace values in the WHERE clause is Substitution variables.
Option A is correct. Substitution variables can be used to replace values in the WHERE clause at runtime. They begin with an ampersand (&) and can be used to replace any part of the SQL query, including the WHERE clause.
Option B is incorrect. Replacement variables are not a feature of SQL*Plus, and they cannot be used to replace values in the WHERE clause.
Option C is incorrect. Prompt variables are also not a feature of SQL*Plus and cannot be used to replace values in the WHERE clause.
Option D is incorrect. Instead-of variables are not a feature of SQL*Plus and cannot be used to replace values in the WHERE clause.