阅读下面文段回答问题。

        I'm Mrs Zhou. I'm a teacher in No. 1 Middle School(第一中学). This is Li Lei. He's Chinese. He is in Class 2, Grade 7. He's my student, and my son(儿子)too. He's twelve.

       That girl is Jean. She's American. She's eleven. And that boy is Jack. He's English. He's ten. They're in Li Lei's class.

I'm their Chinese teacher. All the students and the teachers have two names: an English name and a Chinese name. Li Lei's English name is Tom. My English name is Mary. Their English teacher Miss Jin's English name is Sue. Jean's and Jack's Chinese names are Wei Hua and Zhang Li.

李师傅平均每天加工30个零件，二月份工作22天能加工____个零件。

观光艇满载时以最大航速匀速行驶，此时受到水的平均阻力是多少？

学习了隋唐史后，几位同学做主题演讲，最能准确概括这段历史基本特征的是（    ）