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问题 单项选择题

请选择一组叙述正确的句子（）。

A．鲜蛋保存时，应用水洗净后冷冻保存

B．鲜蛋保存时，采用低温保存，用水洗净，保持干燥

C．鲜蛋保存中有“四怕”即一怕水洗、二怕高温、三怕潮湿、四怕苍蝇叮

D．鲜蛋保存时，应采用冷冻保存

答案

参考答案：C

单项选择题

What is "Walk to School"
Now we are working on a programme of "Walk to School". We would like as many parents and children as possible to take part, even if in a small way. Children who walk to and from school along with their parents can learn essential road safety and life skills.
You can take part by...
■ Walking to and from school with your child every day.
■ Walking for one or two days during the week.
■ Encouraging others to walk, if you already do.
Walking is great!
■ Walking is great exercise! A walk is good for your body and can keep you fit.
■ You won’t have to waste time looking for a parking site.
■ It’s free. You’ll save money by not using the car.
■ It’s pollution-free.
■ It’s a good chance to talk to your children and to meet other parents, too.
Enjoying walking to school!
Here are some suggestions to help you and yore" child enjoy walking to school.
■ Plan a safe route together.
■ Teach children what a kerb is and what it means.
■ Encourage your child to help you choose the safest places to cross the road.
■ Look at and discuss the things you see on your way—especially road signs and what they mean.
Walk to school! Thousands of parents and children already take part, could you
Please go to www. walktoschool, org. uk for more information.

By walking to and from school, children can learn ______.

A. driving skills

B. running skills
C. road safety and life skills
D. knowledge about science
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问答题

一种氢气燃料的汽车，质量为m=2.0×103kg，发动机的额定输出功率为80kW，行驶在平直公路上时所受阻力恒为车重的0.1倍．若汽车从静止开始先匀加速启动，加速度的大小为a=1.0m/s2．达到额定输出功率后，汽车保持功率不变又加速行驶了800m，直到获得最大速度后才匀速行驶．试求：

（1）汽车的最大行驶速度；

（2）当汽车的速度为32m/s时的加速度；

（3）汽车从静止到获得最大行驶速度所用的总时间．
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