单选题 This gold mine was discovered by accident.
  • A. by air
  • B. by chance
  • C. at large
  • D. at ease


【正确答案】 B
【答案解析】[解析] by accident和by chance都表示“偶然”；by air：通过航空的方式；at large：自由的、 不受约束的；at ease：自由自在、放松。