Question

excerpt from stuff matters by mark miodownik (1) in the absence of copper, gold, and meteoric iron, our ancestors tools during the stone age were made of flint, wood, and bone. (2) anyone who has ever tried to make anything with these kinds of tools knows how limiting they are: if you hit a piece of wood it either splinters, cracks, or snaps. (3) the same is true of rock or bone. metals are fundamentally different from these other materials because they can be hammered into shape: they flow, they are malleable. (5) they can harden a blade just by hammering it. (6) and you can reverse the process simply by putting metal in a fire and heating it up, which will cause it to get softer. (7) the first people to discover these properties ten thousand years ago found a material that was almost as hard as rock but behaved like a plastic and was almost infinitely reusable. (8) in other words, they had discovered the perfect material for tools, and in particular cutting tools like axes, chisels, and razors. (9) this ability of metals to transform from a soft to a hard material must have seemed like magic to our ancient ancestors. how should sentence 1 be changed? a delete the comma after gold b change ancestors to ancestors c change stone age to stone age d no change needs to be made. what is the best way to rewrite sentence 5? a not only that, they get stronger when you hit them; you can harden a blade just by hammering it. b you can harden a blade just by hammering it, they get stronger when you hit them, not only that. c not only that a blade gets stronger when you hit them and, by hammering it, you can harden a blade. short answer: rewrite sentence 7 using less words.

Explanation:

1. For the question about sentence 1, the comma after "gold" is unnecessary as "iron, our ancestor's tools during the Stone Age" is a single - descriptive phrase modifying "our ancestor's tools". So, the comma should be deleted.
2. For the question about sentence 5, the original sentence has a convoluted structure. Option C "Not only that, a blade gets stronger when you hit them and, by hammering it, you can harden a blade." re - organizes the ideas more clearly, stating the two properties (getting stronger and hardening) of the blade in a more logical order.
3. For the short - answer part of rewriting sentence 7, we can simplify it to "You can harden a blade by hammering it." which conveys the same meaning in fewer words.

Answer:

1. A. Delete the comma after gold.
2. C. Not only that, a blade gets stronger when you hit them and, by hammering it, you can harden a blade.
3. You can harden a blade by hammering it.