6. the average copper ore mined in 1900 was five percent copper by weight. copper ore mined in 1990 was approximately 0.5 percent copper by weight. what factors could account for this difference? "

The volume of miners and industries using copper in the 20th century presented an exponential growth. Mining tends to extract the highest grade resources first, once they are the most profitable. With the intense activity achieved during the last century, the higher grade non renewable sources were quickly depleted, forcing the industry to start exploring lower grades sources to satisfy the demand.

It is also noteworthy that mining copper of higher quality causes more damage to the environment, having its protocols and restrictions consequently addressed by the legislation. Therefore the costs of mining 5% copper might be outweighed by a higher margin of profit from 0.5% copper which also is less damaging to the environment.

the answer should be:

their party has more members.

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alliances in ww1 were different from ww2 because the entente in ww1 made up of serbia,russia,france,britan,japan and italy later america  and all allied in a sort of balance of power and too keep germany,austria-hungary,and the ottomans down. russia allied the serbians in order to exert its influence in the balkans while france allied the russians because france was still in dismay and insulted after the defeat to the germans during the unification of germany and britian allied the belgians after the germans invasion of belgium.in ww2 the alliances were in a preemptive attempt to deter any further wars into happening while germany and italy allied since they were insulted and humiliated after the previous war while also sharing a similar ideology of facsim along with japan which all 3 had a want for world domination and agreed to assist one another in the endevours 

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