What has been a lasting act of european colonialism

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

In a scientific experiment, a is any factor that can be changed or be changed

The point where two air masses meet is called a