Derek tried his best to hide his laughter, he covered his mouth and cleared his throat. He looked over at Astrid, she was amusing. She reminded him of his foster sister, Ali. She was smart, sarcastic and rude, but he loved her. Derek quickly thought of something else, he didn't like thinking about Ali. It made him sad, and angry all at the same time. Derek took a deep breath and focused on the lesson being taught to them .