赢得朋友有三大法宝：接受对方；赞美对方；重视对方。这一名言告诉我们（    ）

    In the 1880s, Mark Twain managed his own publishing company. He also became interested in various investments（投资）, especially a kind of typesetting machine. He lost almost $200,000 in investments in the machine between 1881 and 1894. Also, his publishing company declared bankruptcy（破产）in April 1894. Thus, in January 1895, Mark Twain found himself publicly shamed by his inability to pay his debts.

    Mark Twain finally recovered from his financial difficulties, through his continued writing and a successful lecture tour in 1895 and 1896. During this much-publicized tour, Twain lectured in such places as India, South Africa and Australia. By the time he returned, he had become an international hero. Twain enjoyed this attention, and his habits of smoking cigars or a pipe and wearing unusual white suits contributed to his showy image. He also made use of his position as a public figure to criticize the US foreign policy.

    Although he was recovering from his financial problems by 1898, Mark Twain had begun to experience tragedy（悲剧）in his personal life. Suzy, his oldest daughter, died of meningitis （脑膜炎）in 1896, while her parents and sister Clara were abroad. In 1903, Mark Twain sold the beloved house in Hartford, which had become too closely associated with Suzy's death. His wife, Olivia, who had developed a heart condition, died on June 5, 1904. His youngest daughter, Jean, died on Dec.24, 1909.

如图甲所示，质量为m=1kg的小物块放在长直水平面上，用水平细线紧绕在半径为R=0.2m的薄壁圆筒上．t=0时刻，圆筒在电动机带动下由静止开始绕竖直中心轴转动，小物块的v﹣t图象如图乙，物块和地面之间的动摩擦因数为μ=0.2．（不计细线在圆筒上缠绕的厚度）则（   ）