题目

                May:Happenings from the past May 5,1884 Isaac Murphy,son of a slave and perhaps the greatest horse rider in American history,rides Buchanan to win his first Kentucky Derby.He becomes the first rider ever to win the race three times. May 9 , 1754 Benjamin Franklin's Pennsylvania Gazette produces perhaps the first American political cartoon(漫画), showing a snake cut in pieces,with the wordsJoin or Dieprinted under the picture. May 11,1934 The first great dust storm of the Great Plains Dust Bowl, the result of years of drought(干旱),blows topsoil all th已知A=-1998×19992000×2001，B=-1998×20001999×2001，C=-1998×20011999×2000，试比较A，B，C的大小．