A Linux administrator has installed a web server, a database server, and a web application on a server. The web application should be active in order to render the web pages. After the administrator restarts the server, the website displays the following message in the browser: Error establishing a database connection. The Linux administrator reviews the following relevant output from the systemd init files:

The administrator needs to ensure that the database is available before the web application is started. Which of the following should the administrator add to the HTTP server .service file to accomplish this task?

A. TRIGGERS=mariadb.service
B. ONFAILURE=mariadb.service
C. WANTEDBY=mariadb.service
D. REQUIRES=mariadb.service