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It’s impossible to live without metals. The main advantage of metals is their strength and toughness. Concrete is used in building because it has steel for strength. Plastics are lighter than metals but they are not usually very strong.
Not all metals are strong. Copper and aluminium, for example, are both fairly weak. But the alloy of these metals, which is called aluminium bronze, is much stronger than pure copper or pure aluminium.
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Concrete is used in building because _______.
it is lighter than metals.
it is not usually very strong.
it has copper for strength.
it has steel for strength.