阅读理解。
In many western schools, sports day is a big event. Children take part in competitive (竞争性的)
sports, trying to break school records and take the first place.
Sports days, or sports meets, are usually held in the warmer seasons, either at the beginning or the
end of the school year. They are also called field days.
Primary school sports days are fun. They usually have activities such as the egg and the spoon race
and the sack race. Other events include the skipping race (跳绳) and the three-legged race. In middle
and high schools, sports days include many of the common track and field events (田径项目). They
are more serious and competitive than primary school ones.
Students' parents and other relatives also come to the school on sports days. They watch children
play. Many schools in the West have "mothers and fathers" races for parents to take part in!
Although sports days are exciting, they also have some problems. According to some reports in the
USA, sports days have become too competitive to be good for students. Some parents put too much
pressure(压力) on the children. Some schools don't have "mothers and fathers" races any more as there
is much fighting and cheating.
短读阅文，回答下列问题。
1. What do children try to do when they take part in sports meets?
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2. When are sports days usually held in the school year?
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3. What are primary school and middle school sports days like?
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4. Who would come to the school to watch children play on sports days?
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5. What does the writer think about sports days?
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B+D在四种不同条件下进行，B、D起始浓度为0，反应物A的浓度（mol/L）随反应时间（min）的变化情况如下表：
