Which of the following is the lowest TCSEC class wherein the systems must support separate operator

Which of the following is the lowest TCSEC class wherein the systems must support separate
operator and system administrator roles?

A.
B2

B.
B1

C.
A1

D.
A2

Explanation:
Reference: pg 129 Hansche: Official (ISC)2 Guide to the CISSP Exam