题目

Robert Spring, a 19th century forger (伪造者), was so good at his profession that he was able to make his living for 15 years by selling false signatures of famous Americans. Spring was born in England in 1838 and arrived in Philadelphia in 1858 to open a bookstore. At first he prospered(繁荣)by selling his small but genuine collection of early US autographs (亲笔签名). Discovering his ability at copying handwriting he began imitating the signatures of George Washington and Benjimin Franklin and writing them on the title pages of old books. To lessen the chance of detection (被发现一个圆柱体和一个圆锥体的体积相等，已知圆锥体与圆柱体的高之比为1：3，那么圆柱体底面积是圆锥体的 [     ]A.B.C.3倍D.9倍