In relation to tests of controls, which of the following expressions is correct?

to. The auditor uses both planned detection risk and tests of control to determine the scope of audit tests to be performed.

b. The greater the control risk, the less evidence that has to be collected to demonstrate the effectiveness of internal controls.

c. When auditors expect to use evidence that was collected in prior periods and that has already demonstrated the effectiveness of certain internal controls, auditing standards require that tests of control be performed every two years.

d. All of the above.