问题
选择题
关于电源的说法，正确的是（ ）
A．电源向外提供的电能越多，表明电动势越大
B．电动势表示电源将单位正电荷从负极移到正极时，非静电力做的功
C．在电源内部从正极到负极电势逐渐提高
D．在电源外部从正极到负极电势逐渐提高
答案
答案：B
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关于电源的说法，正确的是（ ）
A．电源向外提供的电能越多，表明电动势越大
B．电动势表示电源将单位正电荷从负极移到正极时，非静电力做的功
C．在电源内部从正极到负极电势逐渐提高
D．在电源外部从正极到负极电势逐渐提高
答案：B
In 1956 Phoenix, Arizona, was a city with boundless blue 1 . One day as I walked around the house with my sister Kathy’s new parakeet （小鹦鹉）on my finger, I wanted to show Perky what the sky looked like. I took him into the backyard, and then, to my horror , Perky flew off. The enormous, blue sky swallowed up my sister’s blue 2 and suddenly he had gone, clipped wings and all. I told Kathy about Perky's disappearance and I was anxious that she would blame me. But , unexpectedly, Kathy managed to 3 me. With fake optimism, she even tried to convince me that Perky would find a new 4 . But I was far too clever to 5 that such a thing was possible. Decades later, I watched my own 6 growing. We shared their activities, spending soccer Saturdays in folding chairs with the 7 of the kids’ friends, the Kissells. The two families went camping around Arizona together. We became the best of friends. One evening, the game was to tell Great Pet stories. One person claimed（宣称） to 8 the oldest living goldfish. Someone else had a psychic dog. Then Barry, the father of the other family, took the floor and ___9___that the Greatest Pet of All Time was his blue parakeet, Sweetie Pie. "The best thing about Sweetie Pie," he said, "was the 10 we got him. One day, when I was about eight, out of the clear, blue sky, a little blue parakeet just 11 down and landed on my finger." When I was finally able to 12 , we examined the amazing evidence. The dates and the locations and the pictures of the bird all 13 . It seems our two families had been 14 long before we ever met. Forty years later, I ran to my sister and said, "You were 15 ! Perky lived!"
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