What roles do conservation and energy efficiency play in us meet our energy needs using renewable resources?

Gold is not now being extracted from seawater. why not? a. it would be too disruptive to marine life to develop any marine mineral resources b. there is no gold in seawater c. we don't know how to extract minerals from seawater d. it would be too costly and difficult to separate the small amount of gold from the very large amounts of halite and other minerals

At a continent-continent convergence,

The primary agent of contact metamorphism is