SQL injection is a type of attack that occurs when malicious code is injected into a SQL query. This can be done by submitting specially crafted input to a web form or API. The malicious code can then be used to extract data from the database, modify data in the database, or even execute arbitrary commands on the server.

Data Validation is the process of checking user input for malicious content. This can be done by using regular expressions or other techniques to identify and filter out harmful characters. Data validation is an important part of preventing SQL injection attacks, but it is not a foolproof solution.

Secure Cookies can help to protect against SQL injection attacks by preventing attackers from accessing session cookies. Session cookies are used to track user sessions, and they can contain sensitive information such as user IDs and passwords. If an attacker is able to obtain a session cookie, they could use it to impersonate the victim and gain access to the victim's account.

Encryption can also help to protect against SQL injection attacks. Encrypted data cannot be easily read by attackers, even if they are able to inject malicious code into a SQL query. However, encryption is not a perfect solution, as it can be difficult to implement and maintain.

Comprehensive exception handling can help to prevent SQL injection attacks by catching and logging errors that occur during the execution of SQL queries. This can help to identify and fix vulnerabilities in the code that could be exploited by attackers.

The correct answer is A. Data Validation. Data validation is the most effective way to prevent SQL injection attacks. By carefully checking user input for malicious content, it is possible to block most SQL injection attacks before they even have a chance to succeed.

The other options, while helpful, are not as effective as data validation. Secure cookies can help to protect against session hijacking, but they do not prevent SQL injection attacks. Encryption can help to protect data, but it is not a foolproof solution. Comprehensive exception handling can help to identify and fix vulnerabilities, but it is not a preventive measure.

Therefore, the best way to prevent SQL injection attacks is to use data validation. By carefully checking user input for malicious content, it is possible to block most SQL injection attacks before they even have a chance to succeed.