Concept:The correct phrase is a fixed expression used to refer to the time when one century ends and another begins.Explanation:The sentence needs a noun that fits naturally with of the century.The phrase "at the turn of the century" means around the end of one century or the beginning of the next."Turn" is the only option that forms this standard, correct expression.The other choices do not collocate with "of the century" in this context.Answer:B. Turn.