Donna Writes a Check Payable to Tara in the Amount

Donna writes a check payable to Tara in the amount of $2000.00 to pay for her car that she saw for sale on the internet. When Donna sees the car firsthand that Tara is selling she is upset and tells Tara she will only pay her $1000.00. Tara, realizing that her car is pretty much a piece of junk, accepts the check for $1000.00 that Donna altered and cashes it. Shortly thereafter, Tara's friend who proclaims to know everything about the law by what she has read on the internet tells Tara that Donna still owes her an additional $1000.00 as that was the original agreement. Tara contacts Donna demanding the additional $1000.00. What will be the outcome of this issue?

A) Donna owes Tara the additional $1000.00.
B) Since Tara agreed to the varying terms, Donna is discharged from any additional obligation.
C) Donna is not discharged from the additional obligation if the courts determine that the original agreed amount represented the fair market value of the car.
D) Tara must agree in writing to the varying terms before discharge occurs.