Gold was
a. a valuable commodity within nations of west africa
b. not desired by europeans and therefore never mined in west africa
c. never officially found in africa
d. equally shared among the nations of west africa to protect them from invasions of european settlers

The answer is A. A valuable commodity within nations of west Africa

- the gold was desired by the European, The British had to create a colony on the border of Ghana's kingdom just to trade gold, which eliminated option B and C

- Back then, Ghana's kingdom is one of the strongest kingdom on earth so the european have no intention in invading it, so they made a trading agreement with them instead, which eliminated option D.

Answer erosion,oil spills,pollution,tourism,urban development;

The answer is    d.  central highlands