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问题
单项选择题
电力变压器的使用寿命一般是（）年。
A.40～50
B.30～40
C.20～30
D.10～20
答案
参考答案：
C
填空题
从方框中选词并用其适当形式填空。
health, orange,they,China,have
1. The two boys like ____ food, they don't like American food.
2. David ______ got some apples.
3. Vegetables and fruit are ______ food, We should eat them every day.
4. How many ______ are there in the bag?
5. Those are ______ favourite food.
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问答题 简答题
什么是概率分析？概率分析一般有哪些方法？
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