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Yes, Curious, only D works. The reason is the following.
Since the main clause is in the past, the -ing verb that's required after the expression can't help represents the simple past since it's in agreement with the verb in that main clause.
If you use having felt, it really represents the past perfect (had felt), and that doesn't make any sense in this context. The speaker didn't feel sorry for that man before he did whatever he did; it was after he did it or just when he did it. That's why we can't use C.