What would be the best sampling frame for attitude study, when the target population is a. everyone

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Question:

What would be the best sampling frame for attitude study, when the target population is

a. everyone who rode a public transit system last month

b. retail sporting good stores in OR, WA, CA.

c. California citizens over the age of 18.

d. Dwelling units with home espresso machines.

e. people who used unit pricing during a shopping trip in the previous month