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问题 选择题

某学生用示波器观察按正弦规律变化的电压图象时，他将衰减旋钮置于“”挡，将扫描范围旋钮置于第一挡(10～100 Hz)，把同步极性选择开关置于“＋”位置，调节扫描微调旋钮，在屏幕上出现了如图甲所示的正弦曲线，后来他又进行了两步调节，使图象变成如图乙所示的曲线，这两步调节可能是(　　)

A．将衰减调节旋钮换挡并调节标有“↓↑”的竖直位移旋钮

B．将衰减调节旋钮换挡并调节Y增益旋钮

C．调节扫描范围旋钮和调节Y增益旋钮

D．将同步极性选择开关置于“－”位置并调节Y增益旋钮

答案

答案：D

同步极性旋钮控制图像的正余弦，选择-则变成余弦；图像的竖直振幅变大是增大了Y增益旋钮。所以选D。

听力题

根据短文内容及首字母提示,填写所缺单词

In the 1930s, Dan West was farming in Spain.  It was wartime, and people were starving (挨饿). An i小题1: hit him

as he handed out cups of milk to children. “These children don’t need a cup.  They need a cow.” This was the b  小题2: of Heifer International. Heifer International gives different k 小题3:  of gifts.  Its gifts might

say “quack” or “moo”.  Dan West asked friends in the United States to give gifts of heifers(小母牛), or young cows.  S小题4: then, Heifer International has given animals to four million families.  It gives people the chance to f  小题5:   themselves.

Heifers International wants the people they help to help others.  For one project, the group s 小题6:  chickens to some children in Asia.  The children yearned for(向往) the day when they could help others.  Nine-year-old Julie knew she had to look after her chickens w 小题7:  so they would produce new eggs and healthy chicks.  She t 小题8:  good care of them, and they gave birth to strong, healthy chicks.  Julie then passed on the gift of chicks to other families.

Because of Heifer International, children can s 小题9:  their days in a schoolhouse instead of working in the fields.  They can use the money they earn from their animals to pay for school.  Heifer International has made a huge d 小题10:  to people’s lives for many years.  People should be grateful to a kindhearted farmer named Dan West.
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问答题 论述题

人文地理学属于社会学和地理学的交叉学科，具有社会性、区域性、综合性。
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