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Prepared statements are the most appropriate method for safely executing SQL statements in PDO due to their ability to prevent SQL injection attacks. When using prepared statements, the SQL query is defined with placeholders for data inputs, and the actual values are bound to these placeholders separately. This separation ensures that user input is treated as data rather than executable code, which helps maintain database integrity and security.

By preparing a SQL statement in advance, the database engine is able to parse and compile the SQL code without immediately executing it. When the statement is executed, the bound parameters are sent to the database separately. This process ensures that malicious input cannot alter the query structure, significantly reducing the risk associated with executing SQL commands that involve user-supplied data.

In contrast, direct query execution, dynamic SQL generation, and string interpolation do not utilize this level of security. They can allow for the possibility of SQL injection, where an attacker can inject malicious SQL code into the executed query if user inputs are not properly sanitized. Therefore, prepared statements represent a best practice in database interactions using PDO.