You have a web application running on Oracle Cloud Infrastructure (OCI) that lets users log in with a username and password. You notice that an attacker has tried to use SQL comment `--" to alter the database query, remove the password check and log in as a user. You decide to prevent any future attacks. Which of the following OCI services or features would you choose to safeguard your application? (Choose the best answer.) 

Answer options:

A. Network Security Group
B. Data Safe
C. Web Application Framework (WAF)
D. Vault

D