某城市新建一大型自来水厂，为了生产日常生活饮用水，原水采用地下水处理，在地下水处理时发现水色偏黄，负责人见状，为了防止饮用水含有过量的铁元素，于是设置了专门的去除铁的装置，以使达到卫生标准的生活饮用水。
氟化物在自然界中广泛存在，是一种天然的有毒物，当地下水中含氟( )时，长期饮用会破坏牙齿珐琅质而产生斑齿。
A．0.5mg/L
B．0.8mg/L
C．1.0mg/L
D．1.2mg/L
参考答案：C
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| School was over and I was both mentally and physically tired. I sat at the very front of the bus because of my 1 to get home. Sitting at the front makes you 2 out like a shiny coin in a pile of dull pennies. Janie, the driver, tries to break the 3 atmosphere by striking the match of 4 . I try to mind my manners and 5 listen, but usually I am too busy thinking about my day. On this day, 6 , her conversation was worth listening to. "My father's sick," she said to no one in 7 . I could see the anxiety and fear in her eyes. With a sudden change of attitude and interest, I asked, "What's wrong with him?" With her eyes wet and her voice tight from 8 the tears, she responded, "Heart trouble." Her eyes lowered as she 9 . "I've already lost my mum, so I don't think I can stand losing him." I couldn't respond. I was 10 . My heart ached for her. I sat on the old, smelly seat thinking of the great 11 my own mother was thrown into when her father died. I saw how hard it was, 12 still is, for her. I wouldn't like anyone to go 13 that. Suddenly I realized Janie wasn't only a bus driver. That was 14 her job. She had a whole world of family and concerns, too. I had never thought of her as 15 but a driver. I suddenly felt very 16 . I realized I had only thought of people as 17 as what their purposes were in my life. I paid no attention to Janie because she was a bus driver. I had judged her by her job and brushed her off as 18 . For all I know, I'm just another person in 19 else's world, and may not even be important. I 20 not have been so selfish and self-centred. Everyone has places to go, people to see and appointments (约会) to keep. Understanding people is an art. | ||||
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