Which of the following is true concerning related party transactions?

Group of answer choices

a$.$ They are illegal.

b$.$ While not illegal, they generally should be avoided.

c$.$ They are neither illegal nor something to be avoided. They are fine to undertake so long as they help further a firm$$s business objectives and are properly disclosed in footnotes accompanying the financial statements.

d$.$ They are proprietary information that auditors should not ask about due to the Code of Professional Conduct$$s Rules on Client Confidentiality.