Hey artstudent,

I agree with you over the applicability of detection of cancer. Ideally, the from the answer choices its obvious that only Sandra can have cancer but since, option D specifically says that, for me, it scores an additional point there.

Moreover, if you concentrate on the past participle, had, it brings in clarity on sequence of events: Detection of cancer, she could not run for election and thus, her dream was broken. This sequencing is pretty difficult out in B because it just uses simple past using was.

Hope it helps.

Ya...I agree...What is the source of this question...The correct choice definitely implies that Sandra's cancer was running in the mayoral race. This is a classical modifier mistake...