This is clipart converted and broken apart that has been released into the public domain because the document says so, and its from NASA, a USA government agency. The publication is called "The Brain in Space:"
http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/The.Brain.in.Space.html 孩子們在教室裡 astronomy、blackboard、brain、classroom、converted、GGT、government、kids、nasa、pointer、science、space、teacher、usa 天文學、黑板、腦、課堂、轉換、GGT、政府、孩子、上、指針、科學、空間、老師、使用 資料來源:openclipart ( https://openclipart.org/ )