David is a graduate student. One of his essays was published in a well-known scholarly journal. However, Caesar, who is one year David's senior, accuses him of plagiarism. In accordance with the Copyright Act, what measures should Caesar take in order to prove that his copyright was infringed? A. He is older than David, so he can prove the infringement simply by producing his own work. B. He needs to prove that David had access to (the ability to read, reference, or download) his work. C. His copyright took effect at the completion of his work, so he can simply file a claim to prove the infringement. D. He needs to produce his work and identify the similarities between David's essay and his own. (1)AC (2)ABCD (3)BCD (4)BD