下列各代数式中是分式的是（　　）

自然界中的细菌和真菌属于生态系统中的（    ）

圆x²+y²﹣2x+2y=0的周长是（　　）

下图漫画题为“不会被传染！”左边床上的人说：“多么幸运的一件事呀！我们是分床睡的，我不会被传染！” 右边床上依次是：斯大林瘙痒症、希特勒炎症、闪电战瘟疫、纳粹发热病、法西斯流感。下列各项是对此图的分析，不正确的是（   ）

    My uncle is a teacher .He is a  1 man, about 25 years old. He is tall 2  black short hair. He is a very humorous(幽默的) person. He teaches us Chinese. He often  3 us jokes(笑话) and 4to make our class more   5 . In class, he is a very  6  teacher. If we 7  listen to him carefully, he will 8 us some punishment(惩罚) by 9  us some questions.10  after class, he becomes a very good  11 of us. He 12 talks with the girls and plays 13 with the boys.14 of us really like him. He is our 15 teacher.