OEThe blank must be flled with a word that describes the challenge of ensuring unique names under certain limitations. Since these limitations add to the difculty of avoiding duplication, the blank must be flled with choices that reflect the arduousness of this task. To characterize the problem as particularly “acute” or “severe” would do this nicely; both adjectives indicate the added difculty of the problem under the circumstances described, and the pairing renders sentences with similar meanings. None of the other responses describe the difculty of the problem that the rest of the sentence emphasizes.
Thus the correct answer is acute (Choice B) and severe (Choice D).