The letter "A" and "C" can not be correct because Shakespeare did not just use an idea, nor did he maintain the basic meaning of Caesar's commentary in Plutarch's text. So much the less! Shakespeare used the whole theme of Plutaco's narrative as the basis for this passage of his play, so the right answer is the letter D.
Moreover, Shakespeare did not repeat the exact words of Plutarch's biography. He only re-wrote a few, which makes the letter B an incorrect answer.
Most likely teachers because they can talk to the principal about it. Also, it would be helpful to talk to parents so they can tell their kids and talk to other people about it.
