题干

如图表示一交变电流的电流随时间而变化的图象,此交变电流的有效值:(   )

 

A:5 2 A

B:5A

C:2 5 A

D:3.5A

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答案(点此获取答案解析)

C

同类题1

阅读理解

    When Abraham Lincoln was young, he worked in a store. One day a woman came into the store and bought some things. They added up to two dollars and six and a quarter cents.

    The bill was paid, and the woman was satisfied. But the young storekeeper, not feeling quite sure about his calculations(计算), added up the things again. To his surprise, he found that it should have been but two dollars.

    “I've made her pay six and a quarter cents more,” said young Abe, upset.

    It was an unimportant thing, and many salespersons would forget it, but Abe was too careful for that.

    The money must be paid back, he decided.

    At night, he closed the store and walked to the home of his customer. He explained the matter, paid over the six and a quarter cents, and returned satisfied.

    Here is another story of young Lincoln's strict honesty. A woman entered the store and asked for half a pound of tea. The young man weighed it out. This was the last sale of the day.

    The next morning, when beginning his duties, Abe discovered a four-ounce weight on the scales(磅砰). It flashed upon him at once that he had used this in the sale last night, and so, of course, given his customer short weight. Many people would not have been much worried by this discovery. But Abe weighed out four ounces of the tea, shut up the store, and carried it to the customer. I think that the name, so often given in late times to President Lincoln, of “Honest Old Abe", was well deserved(应得的).

同类题4

阅读下面短文,从短文后各题所给的A、B、C和D四个选项中,选出可以填入空白处的最佳选项。

    Everyone loves getting cards on their birthday. For Bailey Sellers, the card from her father is a card, one that she'll 1 forever.

    Her father, Mike Sellers, died of cancer in 2013, just a few months 2 her 17th birthday. But her dad made sure he could still 3 her special day, even in death. Before his death he prepaid a flower shop to 4 flowers and a card to her every year on her birthday. The last flowers and 5 came last week, for her 21st birthday.

    In the card 6 came with this year's flowers, Mike Sellers told his daughter, “This is my 7 letter to you until we meet again. You are and will always be the most precious 8 I was given. I will still be with you through every milestone. Just look around and there I will be.”

    9 by her late father's gesture, Sellers posted a photo of the flowers, the card and an old 10 of her dad raising her up on his shoulder during a long ago trip to the beach.

    “Miss you so much daddy,” the post 11, with a little purple heart. The post moved thousands of people, who not only 12 it but also told their own stories of how they 13 the pain of losing a parent. Sellers 14 that pain; she said she became 15 after her father's death. So now she's studying psychology(心理学), hoping to be able to one day help people get out of the kind of 16 that once enveloped her.

    “He would be so 17 that he pulled off such a beautiful gesture, which offers an important 18 for all of us. He made people 19. He made people realize that they shouldn't take the people who 20 them for granted.”