I guess it's just a matter of how you want to lubricate your synapses. Sitting around and making lists of distinctive features shared by four items in four cases with elimination of one of the four in each of the four cases might be fun if one was so inclined to spend time that way. And how gratifying would be the quest, once realized and achieved. And it sure seems that some kind of computer program could do the job easily--maybe.

But my own synpases are making the request that I oil them with some other kind of oil...maybe some oil that will produce more practical results.

However, kudos to anybody who comes up with the happy result, no matter how trivial.