土壤的酸性太强会带来害虫和疾病，阻碍植物生长，并析出有毒金属。目前，造成我国土壤酸化的主要原因是（）。
A.空气中CO2浓度增大
B.滥施化肥
C.酸雨
D.大面积种植单一作物，生物多样性遭到破坏
参考答案：B, C
解析：
空气中二氧化碳浓度增大会形成温室效应，造成全球气温上升，二氧化碳溶于水生成碳酸（弱酸性），但二氧化碳溶于水达到饱和的pH在5.6左右，不能算酸雨，且碳酸不稳定，容易分解，排除A项。氮肥施用过量是导致农田土壤酸化的主要原因，B项正确。当酸雨输入超过土壤缓冲能力时，土壤就会呈现酸化，使土壤的物理化学性质发生变化，C项正确。生物多样性遭破坏并不会造成土壤酸化，D项错误。
Mental health is about the way you think and feel and your ability to deal with ups and downs. Even though you are mentally healthy, it doesn’t 1 that you don’t have a mental health problem. Mental health is everyone’s business. We all have times when we feel down or 2 . Most of the time those feelings pass, 3 sometimes they develop into a more serious problem. It seems that our mental health doesn’t always stay the same. It can change as the environment changes and as you move 4 different stages(阶段) of your life. Here are four practical 5 to look after your mental health. Making simple changes to how you live doesn’t cost much or take up lots of time. Anyone can 6 them. ●Talk about your feelings. It can help you stay in good mental health. It isn’t a sign of 7 , but part of your ability to do what you can to stay healthy. ●Eat well. What you eat and how you feel are 8 connected. A proper diet can have a good effect on your mental health. ●Keep in touch. Friends and family members can offer 9 suggestions which may help you keep active and solve practical problems. ●Take a break. It could be a weekend 10 new places to enjoy the nature, or even a ten-minute break from doing your homework. A few minutes can be enough to relax you.
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