is still working
has still worked
had still working
was still working
本题考查动词的时态。 由时间状语 when John left the office可知，谓语动词时态应为过去进行时，表示过去某一时刻或某一时间段正在进行的动作，故选D。 句意：约翰离开办公室时，艾米仍然在桌前工作。
