When John left the office, Amy _____ at her desk.

When John left the office, Amy _____ at her desk.
A、is still working
B、has still working
C、had still worked
D、was still working
【正确答案】：D
【题目解析】：when引导的时间状语从句，从句用一般过去时，主句要用过去进行时。