Which of the following statements is correct concerning an auditor’s required communication of significant deficiencies?

a. A significant deficiency previously communicated during the prior year’s audit that remains uncorrected causes a scope limitation.

b. An auditor should perform tests of controls on significant deficiencies before communicating them to the client.

c. An auditor’s report on significant deficiencies should include a restriction on the distribution of the report.

d. An auditor should communicate significant deficiencies after tests of controls, but before commencing substantive tests.