Susan decided not to write her resignation in the office because she didn't want her colleagues to know what she ______.
【正确答案】 C
【答案解析】根据句意，此处要用过去进行时表示过去正在进行的动作。由于decided和didn't want都是过去式，故可排除选项A和D；再者，动作“做”发生在“决定”之后，而不是之前，故不能用过去完成时，答案为C。