Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
Readers familiar with my obsessions may fear that this column is just another attempt to spoil everyone's fun, to replace the beautiful mystery of life with ugly Darwinian clarity. Actually, what I hope to dispel isn't pre-Darwinian mystery, but a kind of post-Darwinian mysticism, a confused exaltation of genetic affinity. You see the confusion when biological parents invoke "blood ties" to reclaim a child from adoptive parents. You see it when opponents of cross-ethnic adoption argue--as in a New York Times op-ed piece a few months ago--that we must respect "the strength of the biological and cultural ties that Indian tribes can offer their own children." In a sense, you see it every year around Christmas, when people pay lip service to the idea of universal brotherhood but believe in their hearts that it's ridiculous, that truly loving people to whom you aren't related violates some law of nature. Thanks to the biologist William Hamilton, it is now clear why people feel brotherly love in the literal sense--and sisterly love, maternal love, and paternal love. It's all due to the operation of "kin selection" during evolution. A greatly oversimplified textbook example: Two million years ago, two hominids, Loveless Bob and Loving Bob, stand on two different riverbanks, in identical situations. Each is watching his full sibling Bill drown. Loving Bob has a gene inclining him to love his brother and thus jump in the raging river, even though his risk of dying is 10 percent. Loveless Bob has no such gene, and thus stands on the bank wondering whether his brother's corpse will attract any large, edible fish. Which Bob's genes will survive the Darwinian reaper--genes for love or for cold indifference? Love triumphs. True, there's a one-in-10 chance that the love gene will sink along with Loving Bob. But consider the upside. There's a one-in-two chance that Bob's full sibling Bill has the same gene and, thus, that a successful rescue mission will pluck an otherwise doomed copy of the gene from the dustbin of history. Do the math, and you'll see that, over time, Loving Bobs send more genes to posterity than Loveless Bobs. As love genes spread at the expense of indifference genes, Loveless Bobs slowly become extinct. Die, selfish scum! Genes for sibling love come to permeate our species--as, in fact, they now do. So do genes for maternal love and paternal love. All brought to you by kin selection. As modern Darwinism gets popularized, the basic idea of kin selection is approaching the status of conventional wisdom. So are some attendant misconceptions. that a gene can magically sense copies of itself in other organisms--or, at least, can somehow ascertain with perfect accuracy which organisms are close relatives of its own host organism and thus may carry copies of itself. In truth, genes aren't omniscient, or even sentient. If kin-selected genes are going to induce love of kin, they'll have to determine who qualifies as kin in some pedestrian and probably fallible way. For example: Back when Loving Bob was 6 years old, if his mother was nursing some infant named Bill and sleeping by its side every night, there's a very good chance that Bill was Bob's sibling. So a gene disposing Bob to love children whom he sees his mother nurturing could spread through the population until everyone obeys the same rule. But this rule would misfire now and then, when a mother is for some reason nurturing a non-offspring. It's just that the misfiring wouldn't happen often enough to greatly dilute the genetic math favoring the gene's proliferation. Little is known about which rules for identifying kin--"kin-recognition mechanisms"--do operate in our species. But clearly, they are fallible. Even mothers, who you'd think would have a damn good idea of who their offspring are, can in principle be fooled. When hospital staffers for some reason handed hours-old Kimberly Mays to a mother who was not hers, the mother's kin-recognition mechanisms--a k a bonding processes--kicked in. This woman wound up loving Kimberly like a daughter (though the mother died two years later, so that Kimberly was reared mostly by a stepmother). Meanwhile, Kimberly's genetic mother, having missed years of bonding, can never love Kimberly quite like her own child, even though Kimberly is her own child. Because genetic relationship per se doesn't matter. Anyway, the main point is that when genetic parents give up a child for adoption and have second thoughts weeks, months, or even years later, their appeals to blood ties should count for zilch. Their love of their child, and their child's love of them, depends not on genetic math but on a long and complex chain of bonding, much of which they have already voluntarily missed out on. Similarly, the idea that Native American babies, or black babies, or whatever, have some mystical genetic affinity with their "own" kind is silly. Obviously, cross-ethnic adoption is dicey. It draws sidelong glances and playground taunts, and it may give the adopted child an identity crisis. But it won't do this because of some ancestral memory in the genes. As attitudes change, cross-ethnic adoption will get easier and as cross-ethnic adoption gets more common, attitudes will change. (There are other pop-genetics arguments against cross-ethnic adoption, and against adoption in general. One is that genes influence personality so powerfully that mixing unrelated siblings is like mixing oil and water. This idea is .) Not that I attach much weight to what is and isn't "good" from the standpoint of genetic self-interest. As virtually all ethical philosophers who have pondered the matter agree, it doesn't make sense to model our moral values on the logic of nature anyway to infer ought from is --to commit the "naturalistic fallacy"--only leads to moral confusion. For example, you might, after observing the natural behavior of praying mantises, be tempted to conclude that it is morally good for females to eat males after sex--and this, I submit, would be a repugnant and wrongheaded doctrine! (Though slightly less repugnant than the idea of eating males before the sex.) Most people implicitly recognize the naturalistic fallacy in some contexts. They sense that there's something visceral about, say, malice yet they'll tell you (when not in its thrall) that they disapprove of it. It's obvious, they believe, that the natural strength of hatred is not a good thing. They're right. What is equally right, but a bit less obvious, is that the "natural" limits of love aren't necessarily good either. And, on close inspection, these limits turn out not to be all that rigorously "natural" anyway.

<question>:
How does the author layer ethics into the discussion of kinship?

<options>:
A Humans have never considered natural behavior in animals to be unethical
B Just because a behavior is natural to animals does not mean it is considered ethical
C Natural behaviors in the animal kingdom always lead humans to do what is ethically “good”
D The ethics discussion is unrelated to the kinship arguments

<answer>:

B