U. S. cities like New York, Los Angeles, San Francisco, and Chicago were formed because of . a.
a natural harbor area
c.
an abundance of animals to hunt
b.
prime agricultural land
d.
pleasant year-round temperatures

The first atomic explosion was detonated in the desert north of alamogordo, new mexico, on july 16, 1945. what percentage of the strontium-90 ( yr) originally produced by that explosion still remains as of july 16, 2016?