What are the advantage of IPSec-based Site-to-Site VPNS over traditional WAN networks?

What are the advantage of IPSec-based Site-to-Site VPNS over traditional WAN networks?

A.
Span, flexibility, security and low cost

B.
Delay guarantees, span, performance, security and low cost

C.
Bandwidth guarantees, support for non-IP Protocols, Scalability and modular design guidelines

D.
Bandwidth guarantees, flexibility, security and low cost