Which of the following statements is true for duress?

a. The reason behind the idea of duress is that mistakes may prevent the "meeting of the minds" required by contract law.

b. The basic idea behind duress is to protect the old, the timid, and the physically or mentally weak from those who gain their confidence and attempt to take advantage of them.

c. The term duress is used in contract law to describe the situation in which one or both of the parties to an agreement acted under an untrue belief about the existence or nonexistence of a material fact.

d. The courts have generally held that the threat of a well-founded civil suit is not duress.