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 the best, choose the first answer; otherwise choose any one of the others.

Although pure diamond is colourless and transparent, but when contaminated with other material, it may appear in various colours, ranging from pastels to opaque black.