Becky Inherited Property from Her Mother Seven Years Ago

Becky inherited property from her mother seven years ago.The property was listed on her mother's estate tax return (Form 706) as having a value of $300,000.Becky is going to sell the property for $800,000,but she believes her real income tax basis is much more than $300,000.Which of the following factors,if any,helps Becky in challenging this basis?

A) She should file an amended Form 706 showing a higher value.
B) She is not certain what the exact value of the property was seven years ago.
C) She was the executor of her mother's estate.
D) The value listed on Form 706 was the result of a negotiated compromise between the IRS and the estate.
E) None of the above.