为调查八年级学生完成作业的时间，某校抽查了8名学生完成作业的时间，依次是：75，70，90，70，70，58，80，55(单位：分钟)，那么这组数据的众数、中位数和平均数依次为(    )．

被誉为“微生物学之父”的是（   ）

Dear Zhou Lan,   

    Thank you very much for your e-mail. I want to go to China. I know something about China from your e-mails. Your English is very good. But I don't know much Chinese. Now I'm learning (学习) it from my parents in the USA. They know much about China. They tell me many things about China.

    I'm happy to know you like your school and your family. You want to know my family and my school. I have a big family. My grandparents and my parents are all very fine. My father has a brother. He is my uncle, John. He and my aunt have their children. They're Bill, Linda, Mary and Lily. My brother Dick is a boy of eighteen. I like my family very much. I'll go to China next year with my mother. She is going to teach English in a middle school in Beijing.

Yours,

               Annie

请写出一个是二次的方程____