Step 1: OCD presents through a small set of recurring obsessional themes, each commonly paired with a matching compulsion that the patient uses to relieve distress.
Step 2: The four well-described patterns are: fear of contamination (paired with washing), doubting whether actions were completed (paired with checking), purely mental intrusive thoughts that are repugnant to the patient, and a need for symmetry or exactness (paired with slowness).
Step 3: Reviewing the options, contamination, pathological doubts, and intrusive thoughts each appear individually as genuine OCD symptom clusters, so no single one can be excluded.
Step 4: Because every listed item is a true major symptom of OCD, the inclusive choice is correct.
$ \text{Contamination} + \text{Doubts} + \text{Intrusive thoughts} \Rightarrow \text{all valid} $
\[\boxed{\text{All the above}}\]