Which of the following is an advantage of software as a service $($SaaS$)$ solutions? A$.$ They reduce or eliminate the need for an on$-$site data center.

B$.$ They eliminate the need for application administration.

C$.$ They allow customers to pay on demand for software use, normally on a per$-$user basis.

D$.$ They offer application, processor, and data storage scalability.

E$.$ All of these are correct.