Step 1: The question asks for a feature that predicts a worse outcome in OCD. Standard psychiatry teaching lists yielding to compulsions, longer duration, early or childhood onset, bizarre compulsions, the need for hospitalisation, comorbid major depression, overvalued ideas, and especially hoarding and a need for symmetry as poor prognostic factors.
Step 2: Among the options, hoarding is the recognised poor prognostic marker. Hoarding-type OCD responds least well to standard SSRI and exposure therapy and carries a more chronic course.
Step 3: Contamination obsessions with cleaning compulsions, by contrast, generally respond well to treatment and indicate a relatively better prognosis, so dirt contamination is not the poor prognostic factor implied by the option key. Pathological doubt and magical thinking are common symptoms but are not the textbook poor prognostic markers asked for here.
Step 4: The medically correct poor prognostic factor among these choices is hoarding, option d, which is why the printed contamination key is overridden.