Who developed one of the first mathematical models of a multilevel-security computer system? 

Answer options:

A. Diffie and Hellman.
B. Clark and Wilson.
C. Bell and LaPadula.
D. Gasser and Lipner.

C

In 1973 Bell and LaPadula created the first mathematical model of a multi-level security system. The following answers are incorrect: Diffie and Hellman. This is incorrect because Diffie and Hellman was involved with cryptography. Clark and Wilson. This is incorrect because Bell and LaPadula was the first model. The Clark-Wilson model came later, 1987. Gasser and Lipner. This is incorrect, it is a distractor. Bell and LaPadula was the first model.