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    Mr. White looks out of his window. There is a boy at the there side of the street. The boy takes some bread out of a bag and begins eating it. There is a very thin dog in the street too.

    The boy says to it, “Come here, good dog. I'll give you some bread.” The dog is hungry and goes to the boy, but he does not give it any bread. He kicks the dog. It runs away.

    Then Mr. White comes out of his house and says to the boy, “I'll give you a shilling.”

    The boy is happy and says,“Yes”. “Come here,” Mr. White says. The boy goes to him, but Mr. White doesn't give him a shilling. He hits him with a stick.

    The boy cries and says, “Why do you hit me? I don't ask you for any money.” “No,” Mr. White says, “And the dog doesn't ask you for any bread, but you kick it.”

堰塞湖是由于火山喷发、地震等原因引起山体岩石崩塌从而堵截山谷、河谷或河床后贮水而形成的湖泊，堵截物质称为堰塞体，往往不够稳定，易形成垮坝。读下图，回答：据图分析，导致图中堰塞湖形成的直接原因是(   )

曲线y=e^﹣x+1在点（0，2）处的切线与直线y=0和x=0围成的三角形面积为（　　）