【正确答案】 B

【答案解析】[分析] 测试点是同义介词短语的用法。at the end of表示“在…的结尾”、“尽头”．in the end of表示“最后、终于”，by the end of用来表示时间。on the end of不符合语法规则。比较：I saw him standing at the end of bridge，(我看见他站在桥的尽头。)He was at the end of his consent．他已智穷力竭了。In the end he gave his consent。最后他同意了。By the end of July，I’ll have read all those books。到七月底以前，所有那些书我就要读完。