Tara was a website designer who was hired by Gus to build a website for his business. Tara would build the site and Gus would provide all the wording and content. In an email exchange with Gus, she agreed to take half the payment upfront and the remaining half of the payment after she had completed the work. She told Gus that if he didn't like the website, he would not owe her the second payment. Upon completion, she sent Gus screenshots of the site and he responded that he didn't like it and wasn't going to make the final payment. Several weeks later, Tara saw that Gus had an active site, with the exact same layout she had designed. The only difference was the color scheme. If Gus took the screenshots of Tara's work and had another designer duplicate it for less cost, which of the following would be Gus's least successful argument that he has not infringed on Tara's intellectual property rights?

a. He hired Tara to make the website.

b. The layout is merely a form on which content is built.

c. He only copied the underlying idea and not Tara's expression of that idea.

d. Tara had not registered her work.