Answer: D) ". . . simple, artless goodness. . ."
Step-by-step explanation: The given phrase "For himself, he is so transparent that all men see him through" gives an idea of a man that is absolutely honest about who he is, he is not trying to hide anything from others, the phrase that is an additional description of John Brown and that has the same meaning is "simple, artless goodness", because it also gives the idea of honest goodness, with nothing to hide, transparent.