A party may have a valid excuse for not performing a contract. Which of the following defenses would be Sylvie's best argument against a contract claim?

Sylvie, a freelance artist, entered into a contract with Yveline to paint a portrait of Yveline's pets. As Sylvie was painting the portrait, Yveline informed Sylvie that she would like Sylvie to incorporate a painting of an image that is copyrighted by another artist. Sylvie consulted a lawyer who advised her that she could not reproduce the copyrighted image without the other artist's permission. Nevertheless, Yveline demanded that Sylvie do as she requested or she would write a scathing Yelp review. After Sylvie refused, Yveline sued Sylvie for breach of contract.

Which of the following defenses would be Sylvie's best argument against Yveline's contract claim?

illegality

duress

condition precedent

incapacity