Had Tom spent as much time studying as he did _______ the computer games, he would have passed the exam.
A.playB.to playC.playingD.played在线课程C
解析：
句意：如果汤姆用在学习上的时间和玩电脑游戏的时间同样多的话，他就会通过考试的。在if引导的非真实条件句中，如果省略了if，那么从句要倒装。as he...games是状语从句，从句中did代替上文spent。根据spend+时间+(in) doing sth.，可知本题选C。