In Which of the Following Situations Will the Court Enforce

In which of the following situations will the court enforce a contract?

A) Tinker offers to sell his car to Evers. Evers asks for some time to decide, and Tinker gives him until 6 p.m. At 4 p.m. Evers sees Chance driving the car and is told that Tinker sold it to him. Evers calls Tinker at 4:30 p.m. and says "I accept."
B) Jan offers to sell his boat to Dean. Dean asks for 24 hours to decide, and Jan agrees. At midnight, the boat sinks, although neither Jan nor Dean knows it has sunk. Dean calls Jan before the 24 hours elapse and says "I accept."
C) Martin offers to sell his horse to Lewis for $1,000. Lewis replies that $1,000 is too much and says, "I'll give you $850 for her." Martin says no, and Lewis replies, "Okay, I'll give you $1,000."
D) Fred offers to sell his car to Wilma. Wilma asks for more time, and Fred says she can have until 10 o'clock the next morning. For Fred to keep the offer open to her, Wilma gives him $50, which is nonrefundable. Fred dies during the night, and after hearing that Fred died, Wilma calls Fred's heirs at 9 o'clock the next morning and accepts Fred's offer.