题目选项分析

Scientists who studied the famous gold field known as Serra Pelada concluded that the rich lode was produced not by the accepted methods of ore formation but that swarms of microbes over millions of years concentrated the gold from jungle soils and rivers and rocks.

Scientists who studied the famous gold field known as Serra Pelada concluded that the rich lode was produced not by the accepted methods of ore formation but by swarms of microbes that over millions of years concentrated the gold from jungle soils and rivers and rocks.