What Documents Must Contain a Statement of Truth and What

What documents must contain a statement of truth and what is the purpose of a statement of truth?

A) Any document that is a 'statement of case'. To ensure that parties tell the truth.
B) Any document that is a 'statement of case' or a witness statement. To ensure that unsupported claims are not made.
C) Any document that is a 'statement of case', a witness statement, an acknowledgement of service, a response to a CPR 18 request, or a certificate of service. To ensure that parties have an honest belief in their claims and to discourage unsupported claims being made.
D) Any document that is a 'statement of case', a witness statement, or response to a CPR 18 request. To ensure that parties have an honest belief in their claims and to discourage unsupported claims being made.