A. works B. is working

C. has worked D. had worked

【答案】C

【解析】句意：丹尼为了实现他的梦想，已经努力了很长时间，现在他很受欢迎。由时间状语for long可知，此处表示从过去开始持续到现在的动作或状态，因此用现在完成时，故选C。