The primary function of the passage as a whole is to:
The best answer is B. The passage describes a marketing strategy practiced by some professional service firms, outlines the arguments in favor of its use, and the describes the drawbacks associated with the strategy.
Choice A is incorrect because the popularity of the practice is not discussed in the passage.
Choice C is incorrect because the passage does not include a demonstration of how to institute unconditional guarantees.
Choice D is incorrect because ethical issues are not addressed by the author.