Keep clean and quiet in the classrooms. Because classroom is a place to study.
在教室里面要保持清洁和安静，因为教室是一个学习的地方。
So that, must carry out the study on technology of clean coal.
因此，必须大力开展洁净煤技术研究。
The study of trace elements was focus of clean coal technology in the world.
煤中微量元素是世界洁净煤研究的热点；
Objective To study the clean production technology of diosgenin.
目的研究黄姜皂素清洁生产工艺。
Objective To study the clean production technology of diosgenin.
目的研究黄姜皂素清洁生产工艺。
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