Residents of Puerto Rico do not pay federal income tax._

Local governments may be limited in how much they can regulate businesses because of the

a. major investment cities have made to keep businesses in their borders. b. amount of corruption found at local levels of government. c. fear of exit that cities have if they lose businesses. d. universal demand for big businesses by citizens.

Suppose we want to test the relationship between trade agreements and wars. The following data were collected. According to these hypothetical data, trade agreements are _______________________ for preventing wars.

a. necessary
b. sufficient
c. necessary and sufficient
d. neither necessary nor sufficient