Excerpt from Stuff Matters By Mark
Miodownik

(1) At some point humans made the discovery that would end the Stone Age and open the door to a seemingly unlimited supply of the stuff. (2) They discovered that a certain greenish rock, when put into a very hot fire and surrounded by red-hot embers turns into a shiny piece of metal. (3) This greenish rock was malachite, and the metal was, of course, copper. (4) It must have been the most dazzling revelation. (5) Suddenly the discoverers were surrounded not by dead inert rock but by mysterious stuff that had an inner life. (6) They would have been capable of performing this transformation with only a few particular types of rock, such as malachite because getting it to work reliably depends not just on identifying these rocks but also on carefully controlling the chemical conditions of the fire. (7) But they must have suspected that those rocks that didn't work, that remained obstinately rock-like however hot the fire became, had hidden secrets. (8) They were right.
(9) Its a process that works for many minerals, although it would be thousands of years before an understanding of the chemistry required (controlling the chemical reactions between the rock and the gases created in the fire) led to the next real break through in smelting.

What change, if any, needs to be made in sentence 6?
• A Change have to has
• B Change reliably to relaibly
• C Insert a comma before but
O D No change needs to be made in sentence

What change should be made in sentence 2? *
• A Change They to We
• B Delete the comma after rock
• C Insert a comma after embers
• D Change shiny to shinny

Find two changes that need to be made in sentence 9.
“Your answer”