According to the Professional Conduct Standards relating to responsibility of supervisors, supervisors are NOT required to:（）
A. take steps to prevent persons acting under their supervision from violating Jaws, rules, regulations, firm policies, or the Code of Ethics and Professional Conduct Standards.
B. contain the firm's compliance procedures in a clearly written and accessible manual that is tailored to the firm's operations.
C. exercise supervisory responsibility to employees who are not CFA Institute members.