His essay, many times,was brief and to the point,and therefore won the first prize in the

网友回答

A. polishing up
B. having polished up
C. to be polished up
(答案→)D. having been polished up
解析：   having been polished up为现在分词完成式的被动式，作定语修饰essay。根据后面的内容可知，他的文章已获得了一等奖，而polish  up (修改，润饰)应是在此之前，故用其完成式。句意为：他的文章，经多次修改后，简洁而又切题，因此在作文比赛中赢得了一等奖。