答案：D

题目分析：去掉“It is”和空格，句子仍然成立，故为强调句。原句：He learns an important lesson: there is no “I” in “team” when a football player has aged and been through many battles.句意：一个足球运动员只有到了他成长大了，并且经历了一些战役后他才能学到重要的一课：团队中没有个体。