求如图所示的交变电流的有效值,其中每个周期的后半周期的图象为半个周期的正弦曲线(

题型:选择题

问题:

求如图所示的交变电流的有效值,其中每个周期的后半周期的图象为半个周期的正弦曲线(   )

A.5A

B.5A

C.5/2A

D./2A

考点:交变电流的周期和频率交变电流的最大值、有效值、瞬时值和平均值
题型:选择题

图A为小岛生态系统食物网简图。有人向小岛引入一定数量的卷尾鬣蜥(主要以沙氏变色蜥和较大的地面节肢动物为食),跟踪调查该生态系统及其对照组的变化,发现沙氏变色蜥和网蜘蛛的数量变化较大(见图B),而其它生物数量变化相对较小。请回答下列问题:

沙氏变色蜥处于第()营养级,其与卷尾鬣蜥的种问关系是().

题型:选择题

在如图所示的各电场中,a、b两点电场强度相同的是  (    )

题型:选择题
阅读下面短文,从短文后各题所给的四个选项A、B、C和D中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。
When I was fifteen, I announced to my English class that I was going to write my own books. Half the students sneered(冷笑), the   nearly fell out of their chairs laughing. “Don’t be silly, only    can become writers, ” the English teacher said, “And you are getting a D this term. ” I was so    that I burst into tears.
That night I wrote a short   poem about broken dreams and mailed it to the newspaper. To my   , they published it and sent me two dollars. I was a published and   writer. I showed my teacher and fellow students. They   . “Just plain dumb luck. ” the teacher said. I tasted   and I’d sold the first thing I’d ever written. That was more than any of them had done and if it was just dumb luck, that was   with me.
During the next two years I sold dozens of   , letters, jokes and recipes. By the time I    from high school, with a C minus average, I had scrapbooks(剪贴簿) filled with my published works. I    mentioned my writing to my teachers, friends or my family again. They were dream killers and   people must choose between their friends and their dreams, they must always choose their     .
I had four children at the time, and the oldest was only four. I wrote what I felt. It   nine months, just like a pregnant woman. I mailed it without a self addressed stamped   and without making a copy of the manuscript(原稿).
A month later I received a(n)   , and a request to start working on another book. The worst year I earned two dollars. In my best year I earned 36, 000 dollars.      years I earned between five thousand and ten thousand. No, it isn’t enough to live    , but it’s still more than I’d make working part time. People ask what college I    , what degrees I had and what qualifications I have to be a writer. The answer is: “None. ” I just write. I’m not a genius.
小题1:
A.wholeB.otherC.mostD.rest
小题2:
A.generals B.statesmenC.geniuses D.spies
小题3:
A.delighted B.anxiousC.ashamed D.upset
小题4:
A.sad B.innocentC.disappointing D.puzzled
小题5:
A.delight B.astonishmentC.comfortD.happiness
小题6:
A.borrowed B.lent C.paid D.cost
小题7:
A.cried B.agreed C.swore D.laughed
小题8:
A.failureB.successC.coldness D.squeeze
小题9:
A.fineB.mixed C.compared D.full
小题10:
A.books B.poets C.novels D.poems
小题11:
A.dropped out B.leftC.graduated D.laid off
小题12:
A.ever B.never C.seldom D.even
小题13:
A.if B.unless C.until D.before
小题14:
A.teachers B.familyC.friendsD.dreams
小题15:
A.spent B.costC.tookD.wasted
小题16:
A.letter B.envelopeC.writer D.cover
小题17:
A.agreementB.editionC.tradeD.patent
小题18:
A.RecentB.MemorableC.Most D.Several
小题19:
A.with B.onC.by D.in
小题20:
A.deservedB.introducedC.founded D.attended
题型:选择题

驾驶人在实习期内驾驶机动车时,应当在车身后部粘贴或者悬挂统一式样的实习标志。

题型:选择题

中共四大的中心议题是()。

A.提出民主革命纲领

B.讨论国共合作,建立革命统一战线问题

C.讨论党如何领导即将到来的革命高潮

D.批评了陈独秀"右倾"错误,强调了同资产阶级争夺领导权的重要性

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