Though trying really hard, they acknowledged at last.
A. defeated
B. defeating
C. having defeated
D. having been defeated
网友回答
A. defeated
B. defeating
C. having defeated
(答案→)D. having been defeated
解析：考查acknowledge用法。承认做某事acknowledge doing sth. acknowledged having done表示动作已经发生
句意为，尽管很努力地尝试了，他们还是最终成人被打败了。