Excerpt from Stuff Matters By Mark Miodownik

In the absence of copper, gold, and meteoric iron, our ancestors’ tools during the Stone Age were made of flint, wood, and bone. 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. 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. Not only that, they get stronger when you hit them; you can harden a blade just by hammering it. And you can reverse the process simply by putting metal in a fire and heating it up, which will cause it to get softer. The first people to discover these properties ten thousand years ago had found a material that was almost as hard as a rock but behaved like a plastic and was almost infinitely reusable. In other words, they had discovered the perfect material for tools, and in particular cutting tools like axes, chisels, and razors. This ability of metals to transform from a soft to a hard material must have seemed like magic to our ancient ancestors.

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In 1961 Professor Richmond from Oxford University discovered a pit that had been dug by the Romans in AD 89. It contained 763,840 small two-inch nails, 85,128 medium nails, 25,088 large nails, and 1,344 extra-large sixteen-inch nails. The hoard was of iron and steel and not gold, which most people would have found bitterly disappointing. But not Professor Richmond. Why, he asked himself, would a Roman legion bury seven tons of iron and steel? The legion had been occupying the advance headquarters of Agricola in a place called Inchtuthil in Scotland. This was at the outer reaches of the Roman Empire, and their mission was to protect its border from what they saw as the savage tribes who threatened it: the Celts. The legion of five thousand men occupied the region for six years before retreating and, in the process, abandoning their fort. They made great efforts to leave behind nothing that could help their enemies. They smashed all food and drink containers and burned the fort to the ground. But they weren’t satisfied with this. In the ashes were the steel nails that had held the fort together, and they were far too valuable to be left to the tribes that had driven them out. Iron and steel were the materials that enabled the Romans to build aqueducts, ships, and swords; they allowed them to engineer an empire. Leaving the nails to their enemies would have been as useful as leaving a cache of weapons, so they buried them in a pit before marching south.
The author draws a contrast between metals and other materials in all of the following EXCEPT:

A) Flint, wood, and bone are more brittle.

B) Metals are reusable.

C) Metals are non-polluting.

D) Metals can be shaped into other objects.