题目

十五边形从一个顶点出发有 （ ）条对角线． A．11   B．12   C．13   D．14 答案：B．【解答】解：n边形（n＞3）从一个顶点出发可以引（n﹣3）条对角线，所以十五边形从一个顶点出发有：15﹣3=12条对角线． 句型转换 A：Mr．John made his living by selling newspapers until the 1960s． B：Mr．John ________　________　________　________ by selling newspapers until the 1960s．