impulse /??mp?ls/ n. 冲动；刺激；推动力
■ answer sb. back 表示“和某人顶嘴”。例如：He's a rude litte boy, always answering his mother back.（他是一个没礼貌的小男孩，总和他母亲顶嘴。）
聚集在老师周围 flock around one's teacher
A：The children flocked around their teacher.
孩子们聚集在他们的老师周围。
B：They were attracted deeply by the story the teacher told.
他们被老师讲的故事深深地吸引住了。
flock /fl?k/ v. 聚集，聚结
向老师解释某事
explain something to one's teacher
