45. May: Happenings form the PastMay 5, 1884Isaac 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, 1754Benijamin Franklin’s Pennsylvania Gazette produces perhaps the first American political cartoon(漫画)，showing a snake cut in pieces with the words “John or Die ” printed under the picture.May 11, 1934The first great dust storm of the Great Plains Dust Bowl, the result of years of drought(干旱)，blows topsoil all the way to New York City and Washington, DCMay 19, 1994Jacqueline Lee Bouvier Kennedy Onassis, form first lady and one of the most famous people of the 1960s, died of cancer in New York City at the age of 64.May 24,1844Samuel F.B Morse taps out the first message, “What hath God wrought,” over the experimental long-distance telegraph line which runs from Washington,DC, to Baltimore, Md.We know from the text that Buchanan is .
(A) Isaac’s father
(B) a winning horse
(C) a slave taking care of horse
(D) the first racing horse in Kentucky