Mr. S, a dealer of musical instruments, persuades me to buy an electronic organ, orally promissing that I can return the organ if I cannot learn how to play it. I signs a standard written form contract, which does not include this provision. I will not be able to testify as to Mr. S's oral promise, because such testimony is prohibited by what?

Question

a. Statute of Frauds
b. Statute of Limitationss
c. The Parole Evidence Rule
d. The general rule for the interpretation of the contract

I think #D