Indicate which of the following statements is TRUE with respect to internal controls. (check all that apply)

Select one or more:

a. The components of internal control are built on the foundation of the ethical tone set by the company's outside auditors.

b. Historically, employee tips have been the most common means of detecting employee fraud.

c. Fraud committed by lower-level employees is more difficult to detect because those employees more often have the ability to override internal control procedures.

d. Collusion refers to the act of two or more individual circumventing internal control procedures.