问题
单项选择题
频率特性指当（）电压幅度恒定时，电路的输出电压随输入信号频率而变化的特性。它是发射机、接收机等电子产品的主要性能指标。
A.输出信号
B.电路中任意信号
C.输入信号
答案
参考答案：C
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频率特性指当（）电压幅度恒定时，电路的输出电压随输入信号频率而变化的特性。它是发射机、接收机等电子产品的主要性能指标。
A.输出信号
B.电路中任意信号
C.输入信号
参考答案：C
Early one morning, an old woman was carrying a big basket of potatoes on her head to the market. She hoped to them to the people from town. The mountain road was narrow (窄的) and the old woman was walking , because she did not want to have and lose her potatoes. Suddenly she a loud bell, and a bicycle came round the corner. It passed her and went very fast the hill. The old woman had to jump to one side of the so quickly that the basket of potatoes nearly fell into the valley (山谷). She looked up and saw that a young boy was on the bicycle. He was on without even round to see whether the old woman was all right. The old woman began to shout, “Come back, young man! You dropped something!” When he heard this, the boy stopped the bicycle so suddenly that he nearly fell off. Then he turned and began to the bicycle back up to the hill. “What is it?” he asked, “What did I drop?” “Little boy,” the old woman answered, “you dropped your .”
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