The correct option is C It is a useful but problematic ethical theory.
The author is critical of utilitarianism, but she also includes evidence that it is a useful theory. LeGuin’s story, for example, shows how the sacrifice of one can create the happiness of many. The author also notes that “many useful social policies and much legislation are founded on” utilitarianism, demonstrating that it is a useful ethical theory. The word choice throughout also indicates that the author feels that this ethical theory has both positive and negative aspects. For example, she calls it “problematic,” but not “wrongheaded” or “faulty.” She calls the problem of the suffering of the few for the happiness of the many a “dilemma,” not a “flaw” or “failure.” She asks questions rather than making statements about the immorality of utilitarian choices. Choice a is incorrect because it simply states a fact from the essay; it does not express an opinion. The author clearly states that “there are several serious problems with utilitarianism as a basis for morality,” so choice b is incorrect. Although the statements in choices d and e are true and clearly stated in the text, these are specific criticisms of utilitarianism and do not sum up the author’s opinion of this ethical theory.