According to the Codes of Ethics for professional accountants, which of the following statements is an element of the principle of 'objectivity':

a. Accountants must be straightforward and honest in professional and business relationships.

b. Accountants must not compromise their professional judgement because of bias.

c. Accountants must disclose information if there is a professional duty to do so.

d. Accountants must not compromise their business judgement because of undue influence of others.