$1.$ The design principles discussed in this module are important because by following them, we can ensure a$.$ correctness of the TCB$.$ b$.$ reduced likelihood and impact of an attack. c$.$ better performance for the TCB$.$ d$.$ automation of security.

$2.$ An electronic health record $($EHR$)$ system purchased by a hospital system comes with default permissions set such that any healthcare worker $($e$.$g$.,$ doctors, nurses etc.$)$ is allowed to access any patient record. This EHR system violates the following design principle. a$.$ Defense$-$in$-$depth b$.$ Separation of privilege c$.$ Failsafe default d$.$User acceptability $3.$ Least common mechanism is another design principle that states a system should minimize the number of mechanisms that allow different applications to interact with each other. This is motivated by the following. a$.$ Interaction between mutually untrusting applications potentially allows a compromise in one to propagate to another one. b$.$ Adding more common mechanisms could increase system complexity. c$.$ Isolation is good for security which could potentially be overcome by an insecure common mechanism. d$.$All three of the other answers $4.$ Safe deposit boxes in banks require two keys to unlock them. One of the keys is held by the bank and the other key is made available to the safe deposit box owner. From a security perspective, this is explained by the following design principle. a$.$ User acceptability b$.$ Separation of privilege. c$.$Least privilege. d$.$ Failsafe default $5.$ In popular operating systems, privileges are associated with user or group identifiers. This allows any process running on behalf of a user U to access all resources to which U has access. This could violate the following design principle. a$.$ Failsafe default. b$.$Open design.

c$.$ Least privilege. d$.$ User acceptability.