题目

阅读理解 It's seven fifty in themorning. The students are coming into the classroom. A boy is opening thewindow. Some of the students are laughing and talking. Some are reading books.Some are doing their homework. Miss White is standingbehind the teacher's desk. She is writing on the blackboard. Lucy and Lily arewearing their new dresses today. Mary is cleaning her desk. Jim is helping her.They all look happy. What are John and Tomdoing? Oh, dear! They are still playing football on the playground. （1） The students are _______. A . at school B . at home C . in the classroom D牛奶中的蛋白质是由母牛的乳腺细胞合成分泌的，与此生理功能相关的细胞器有 A．线粒体、内质网、中心体、高尔基体  B．核糖体、中心体、内质网、高尔基体 C．线粒体、核糖体、内质网、高尔基体  D．线粒体、核糖体、中心体、高尔基体