Ethan fraudulently induces Franz to sign a promissory note to buy a speedboat. Franz’s friend, Gus, agrees to act as a guarantor of the note. If Franz fails to make payment to Ethan, with respect to the defense of fraud, Gus can

a. assert this defense against Ethan.

b. assert this defense against Franz.

c. assert this defense against no one.

d. assert this defense against either Ethan or Franz.