$1.$Most widely used operating systems provide considerable support for auditing but do not implement mandatory access control.What is the highest TCSEC class in which this system can be placed? a$.$C$1$ b$.$ B$1$ c$.$D d$.$C$22.$SELinux is a security enhanced Linux system.It can be placed in the B$1$ TCSEC class because it enhances standard Unix with the following a$.$discretionary access control b$.$logging$/$auditing c$.$mandatory access control d$.$ formal correctness $3.$ seL$4$ claims to be the world's most high$-$assured operating system kernel $($OS kernelcan be viewed as the TCB$).$ This claim could be based on a$.$ better performance of seL$4$ b$.$ multi$-$factor user authentication in seL$4.$ C$.$ formal proof for the correctness of seL$4$ d$.$none of the above