In the text below some words are missing. Select appropriate words to fill the gaps.

Gunpowder, also referred to as ‘black powder’, was the only known chemical (1) ……………. until the mid-nineteenth century. It (2) ………………….. I potassium nitrate, or ‘saltpeter’, which is an oxidizer, and a (3) ……………….. of charcoal and Sulphur serves as fuel. There is an academic consensus that gunpowder was initially (4) …………………… in China as early as the ninth century. This led to its (5) ………………….. in fireworks and in gunpowder weapons.

(1) unique (2) combination (3) drastic (4) changing (5) invented (6) contains (7) explosive (8) use

« Previous                                            21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40                                         Next »