Directions: This question presents a sentence, all or part of which is underlined. Beneath the sentence you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

The essence of iteration is the ability to hear one acoustic blast as a repetition of the form of another, without it being the case that necessary and sufficient conditions for repetition can be stated in advance.