Which of the Following Expresses a Correct Principle of Law

Which of the following expresses a correct principle of law?

A) Failure to disclose facts when there is a duty to reveal them, does not constitute fraud.
B) Violence or intimidation does not render a contract annullable if employed not by a contracting party but by a third person.
C) A threat to enforce one's claim through competent authority, if the claim is legal or just, does not vitiate consent.
D) Simulation of a contract always results in a void contract.