The requirements for a web application state that it must be architected for high availability. The web application consists of front-end web server and back-end database server components respectively. Which of the following describes a solution that meets this requirement, while minimizing costs?

A.
One front-end web server and two clustered back-end database servers

B.
Two front-end web servers and two back-end database servers

C.
Two front-end web servers and one back-end database server

D.
Two load balanced front-end web servers and two clustered back-end database servers