问题
选择题
His essay, ____many times,was brief and to the point,and therefore won the first prize in the writing competition.
A．polishing up
B．having polished up
C．to be polished up
D．having been polished up
答案
答案：D
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。