You Owe Mr

You owe Mr. Store $900 for goods received and want him to take $800 in full satisfaction of the debt. Which of the following is false?

A) If he agrees with you and does take the $800, even if it is paid early at his request, he can still later sue you for the $100 forgiven. His promise not to demand the $100 from you was a gratuitous promise and therefore not binding.
B) If he actually takes the $800 in full satisfaction of the debt, statute law in many jurisdictions prohibits him from suing you for the $100.
C) If you pay the $800 before the actual due date in consideration for his taking this as full payment, he cannot sue for the other $100.
D) If Mr. Store agreed to take the $800 as full payment, but before taking it changed his mind, he would be entitled to the entire $900.
E) If Mr. Store agreed to take the $800 as full payment in exchange for your promise to sweep the floor of his store, he cannot sue for the $100.