A: The rat can experience regret.
That was my first thought, when I learned that scientists have discovered that rats can experience regret.
However, if you read the story, the differences between the rodent and the politician vanish, since the experiment observed the rat’s reaction to learning that he had missed out on a better meal. So this species of regret is the kind a politician does suffer, when he realizes he didn’t fully devour from the public trough the best that was available at the moment.
The scientists did not establish that the subject feels regret for the harm he has done, for how he has nibbled away the substance of his host organisms, for the way he has placed his appetite ahead of the needs of others, for how he has soiled the house and spread all manner of loathsome ailments.
One day, perhaps, science will discover such a conscience…in the rat.