According to the passage, which of the following is true about human-generated air pollution in localized regions?
A.It can be dwarfed by nature's output of pollutants in the localized region.
B.It can overwhelm the natural system that removes pollutants.
C.It will damage areas outside of the localized regions.
D.It will react harmfully with naturally occurring pollutants.

According to the passage, the numerical valued of the concentration level of a substance is only useful if ___________ .
A.the other substances in the area are known
B.it is in a localized area
C.the naturally occurring level is also known
D.it can be calculated quickly

Which of the following is best supported by the passage?
A.To effectively control pollution local government should regularly review their air pollution laws.
B.One of the most important steps in preserving natural lands is to better enforce air pollution laws.
C.Human activities have been effective in reducing air pollution.
D.Scientists should be consulted in order to establish uniform limits for all air pollutants.

What does the word "sensitive " mean?
A.logical
B.responding
C.cautious
D.friendly

It is a waste when customers buy low-quality products because _______.
A.they are very cheap
B.they will soon throw them away
C.they have to be repaired many times
D.customers always change their idea

What best describe the process of reuse?
A.The bottles are washed, returned filled again and collected.
B.The bottles are collected, washed, returned and filled again.
C.The bottles are collected, returned, filled again and washed.
D.The bottles are filled again after being returned, collected and washed.

What are the two things mentioned as examples of recycling?
A.Hamburger wrappings and spent motor oil
B.Aluminum cans and plastic wrappings
C.TV sets and aluminum cans
D.Aluminum cans and spent motor oil

The word "practice " is closest in meaning to _______.
A.training
B.deed
C.exercise
D.belief

Gardeners transplant bushes and flowers by moving them from one place to ______.
A.other
B.others
C.the other
D.another

The author characterizes the growth of new large cities in the United States after 1900 as resulting primarily from ______________ .
A.new economic conditions
B.images of cities shown in movies
C.new agricultural techniques
D.a large migrant population