In Which Circumstance May a Court Find Parol Evidence Admissible

In which circumstance may a court find parol evidence admissible to further the court's understanding of an agreement?

A) When a court determines that there is significant disagreement regarding the complete and final version of the agreement.
B) When a court determines that a written agreement does not represent a complete and final version of the agreement.
C) When a court determines that there is disagreement between the parties' over performance of the agreement once performance has actually started.
D) When a court determines that the plaintiff failed to do sufficient research to determine if signing the agreement was advisable.
E) When a court determines that either party failed to do sufficient research to determine if signing the agreement was advisable.