Identify the key directives introduced by the Sarbanes$-$Oxley Act to enforce the independence of auditors. $($Check all that apply.$)$

It requires senior auditors to rotate off an account every two years and junior auditors every four years.

It mandates auditors to reveal all written communications between management and themselves.

It necessitates an external auditor to report to a client's audit committee on specific issues.

It forbids a public accounting firm from auditing a company whose controller was employed by that firm within the past two years.