The base package including point class, line class, area class, volume class, complex object class and relation class, is the base of the application package and the combination package.

其中基础类包是应用类包和组合类包的基础，它用点、线、面、体、复杂对象和关系类等基本的要素表示三维空间。

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The post office has promised to resume first class mail delivery to the area on Friday.

邮局已承诺在星期五恢复该地区第一类邮件的递送。

《柯林斯英汉双解大词典》

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I've read a lot of research in this area about the importance of quiet times whether it's in a class, in a lecture, whether it is at home, whether it is for a leader in the business, for relationship, for children starting from pre-schools.

关于安静时刻的重要性，无论是课堂里，讲座里，还是家中，无论是对公司领导，爱情关系，甚至学龄前儿童。

哈佛公开课 - 幸福课课程节选

Developers hope improvements will attract new buyers, especially young professionals and families, to a traditionally working-class area.

WSJ: London Developers Hope for Olympic-Size Boom

Standing outside her house in a middle-class area about 45 minutes from Argentina's capital, she laughed Monday as she described his comments.

CNN: March 18, 2013 -- Updated 2111 GMT (0511 HKT)

"It's a safe, quiet, upper-class area, " he told the BBC.

BBC: Paris primary school shooting: Man kills himself