I believe the answer is: The control group would be cars that were washed by hand
The control group exist in order to measure the result that created by subjects that recieve specal treatment (the special treatment in this case would be the automated car wash).
In the example above, the result from automatic car wash would be controlled by comparing it to the result from handwashed cars.
The structures would make the people there more economy by stimulating it with workers and it would help socially as it would build communities
The important part here is "daily" - so we can ask, what else happens daily? the seasons, which are caused by the tilt of the earth and the Earth's rotation around the Sun, are on a yearly schedule rather than a daily schedule. What happens on a daily basis is one rotation of the Earth on its axis - and the correct answer is a)
