In recent years, many Indian reservations have begun increasing their revenues by relying on:

How does the model of tradable pollution rights work?

a) The government charges firms for each unit of pollution they emit; a unit can be traded for a tax break. b) Government and industry leaders agree on maximum emissions standards, firms can trade lower standards for government subsidies. c) Firms who emit less than the industry standard are given certain bargaining privileges. d) Firms are given permits allowing a certain amount of emissions, which can be bought and sold

The logic of an experiment is that when one group that experiences an experimental manipulation and another group does not, any differences in subsequent behavior are due to the independent variable. This conclusion is true when

a. both groups are comparable at the beginning of the study. b. the control group and the placebo group experience the same manipulation. c. the study is double-blind, but not single blind. d. demand characteristics are present in both groups.