Charlie studied in a famous college for four years. He studied hard and did well in all his subjects. He hoped to become a good teacher. This year he left the college and began to work in a middle school. He likes his students and is strict with them. He does his best to make his classes lively and interesting.

    One day he carefully explained a chemical reaction to the students of Grade 2 in the chemistry lab.

    “Be careful, everyone,” he said loudly. “Before I make the experiment, there're twenty five atoms of carbon (碳原子), but after I finish it, there're twenty four atoms of carbon left!”

He stopped to watch the classroom and hoped his students would go on explaining it. But the young men looked at each other and nobody answered him. He had to ask,

    “What happens? What makes the atom lost?”

    The classroom was very quiet and none of the students looked at their teacher.

    “Who can tell us where it has gone?”

    Suddenly a soft voice came from the back row, “We did not see anybody leave the lab!”

    There are forty-eight students in our class. There are twenty-three boys and twenty-five girls. Some students live near the school, and some others live very far from the school. About half of the students come to school by bike. They often get to school at a quarter to seven. About ten students often come to school by bus. They often go to school very early, too. Another ten students come to school on foot. Their homes are near the school, but they are often late for school, because they get up very late.

“世上创痍，诗中圣哲；民间疾苦，笔底波澜。”这是郭沫若对哪位古代著名诗人的评价（　　）