An opinion poll is to be conducted among cable TV viewers. Four multiple-choice questions, each with three possible answers, will be asked. In how many different ways can a viewer complete the poll if exactly one response is given to each question?

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This is a rule of product question . The correct answer is 81 different ways thus B is the correct answer . To state it simply if you have a ways to select something from a set , and b ways to select something from another set you have a * b ways for both . It applys for any given number of sets . In this case its 3 * 3 * 3 * 3 = 81

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