题干

从4台甲型和5台乙型电视机中任意取出3台,要求至少有甲型与乙型电视机各1台,则不同的取法共有(  )

A:140种

B:84种

C:70种

D:35种

上一题 下一题 0.0难度 选择题 更新时间:2018-09-02 07:24:34

答案(点此获取答案解析)

C

同类题2

阅读理解

    In 1999, twelve percent of public elementary schools in the United States required students to wear uniforms. Just three years later, the amount was almost double that.

    A study of six big-city Ohio public schools showed students who were required to wear uniforms had improved graduation, behavior and attendance rates. Academic performance was unchanged.

    Some high schools in Texas have also joined in the movement. Yet studies find mixed results from requiring uniforms. And some schools have turned away from such policies.

    Supporters believe dressing the same creates a better learning environment and safer schools. The school district in Long Beach, California, was the first in the country to require uniforms in all elementary and middle schools. The example helped build national interest in uniforms as a way to deal with school violence and improve learning.

    Findings in Long Beach suggested that the policy resulted in fewer behavior problems and better attendance. But researcher Viktoria, who has looked at those findings, says they were based only on opinions about the effects of uniforms.

    She says other steps taken at the same time to improve schools in Long Beach and statewide could have influenced the findings. The district (the area marked by government) increased punishments for misbehavior. And California passed a law to reduce class sizes.

    In Florida, for example, researcher Sharon found that uniforms seemed to improve behavior and reduce violence. In Texas, Eloise found fewer discipline problems among students required to wear uniforms, but no effect on attendance.

    Sociologist David has studied school uniform policies since1998.He collected the reports in the book. In his own study, he found that reading and mathematics performance dropped after a school in Pennsylvania(宾夕法尼亚州)required uniforms.

    Political and community pressures may persuade schools to go to uniforms to improve learning. But David and others believe there is not enough evidence of a direct relationship. In fact, he says requiring uniforms may even increase discipline problems.

根据短文内容,选择最佳答案,并将选定答案的字母标号填在题前括号内。

同类题4

完形填空

    Twenty years ago, I drove a taxi for a living. One early morning, I1 a call for a taxi. When I arrived at the building, it was 2:30 a.m. and I found the building was dark except for the only light in a first floor window.

    Many drivers would just shout once or twice and then drove away, but I thought this 2 might need my help. So I walked to the door and knocked, “Just a minute,” answered a3, elderly voice. After a long time, the door opened. A small old man showed up before me,4a small bag. He kept thanking me for my5. “It's nothing,” I told him.

    “Oh, you're such a good man.” He said. When we got into the taxi, he gave me a (an)6, and then asked, “Could you drive through the city center?”

    “But it wasn't the7way.” I answered quickly. “Oh, I'm in no hurry.” He said. “I'm on my way to a hospital. I don't have any family left. The 8 says I don't have much time left.

    I 9 started the taxi and shut off the meter(计程器). For the next two hours, we drove through the city center. He showed me the building where he once worked. We drove10 the church where he got married. He would never forget that happy moment. Sometimes he'd ask me to slow down in front of a building and would sit11the darkness for a long time, saying nothing. When the sun began to rise, we drove in silence to the address he had given me. When we arrived,12 without thinking, I gave him a big hug. “You gave an old man a little moment of13. Thank you!” He said with tears in his eyes.

    I was completely lost in thought for the rest of the day. What would happen if I had refused to do14 I did? We always think that there are no15 moments in our lives, but great moments are just in what others may think small and unimportant ones!