Shortly after the accident two police were sent to the spot to keep order . A. dozens o

问题补充：

Shortly after the accident , two police were sent to the spot to keep order .

A. dozens of

B. dozens

C. dozen of

D. dozen

答案：

A. dozens of

B. dozens

C. dozen of

(答案→)D. dozen

解析：英语中一些表示数字的名词的前面如果用了数词，这些名词必须是单数形式，如dozen(一打)，score(二十)和head (头) 等，例如：另外两打鸡蛋another two dozen eggs ; 八十七年前four score and seven years ago ; 五十五头牲口fifty-five head of cattle 。但是如果这些名词用来虚指某些可数名词时，这些名词呈复数形式，其后更加上介词of例如：dozens of pencils (几十支铅笔)和scores of tame birds (几十只家禽)。