The Biba and Clark-Wilson access control models are used in the commercial sector. The Biba model is a formal state transition system of computer security policy that describes a set of access control rules designed to ensure data integrity. Data and subjects are grouped into ordered levels of integrity. The model is designed so that subjects may not corrupt data in a level ranked higher than the subject, or be corrupted by data from a lower level than the subject. The Clark-Wilson security model provides a foundation for specifying and analyzing an integrity policy for a computing system. Answer: D is incorrect. The Bell-LaPadula access control model is mainly used in military systems. Answer: B is incorrect. There is no such access control model as Clark-Biba.