Answer:
There should always be a control group when testing with different peoples. A control group does not receive any variable/treatment. This helps the geneticists to compare the results between control group and the group that's being tested.
His insistence that the Kaiser must step down
Boulder Dam
Explanation:
Hoover dam, named after president Herbert Hoover, was originally called Boulder Dam after the name of the labor colony built in the vicinity of the dam for the workers. It is located in the black canyon of the Colorado River near Boulder City at the borders of the U.S. states of Nevada and Arizona.