he correct answer is C, vSphere HA Restart Priority.
vSphere HA Restart Priority allows you to specify the order in which virtual machines are restarted after a host failure. This can be used to ensure that critical virtual machines are restarted first.
In the scenario described, the database server is the most critical virtual machine, followed by the application server, and then the Web server. You would therefore set the restart priority for the database server to 1, the application server to 2, and the Web server to 3.
This would ensure that the database server is restarted first, followed by the application server, and then the Web server. This would minimize the impact of the host failure on the three-tier application