Which of the Following Statements Is Correct About Non-Executive Directors

Which of the following statements is correct about non-executive directors?

A) A grey director is a non-executive director who may,at times,experience a conflict of interest because of their positions with other organisations;
B) Non-executive directors must be independent;
C) Listed companies must have at least one non-executive director on their board;
D) Non-executive directors do not have the same powers as executive directors.