Which of the following is the least useful kind of relationship in social science theory?

In recent years, unions have found it difficult to win congressional backing of the Employee Free Choice Act, also known as “card check.” What is this bill about?

What will be an ideal response?

One of the most convincing explanations for the persistence of the two-party system in the United States lies in its use of which of the following?

A. Single winners chosen by an absolute majority of votes B. Multiple winners chosen by a proportional representation of votes C. Multiple winners chosen by a simple plurality of votes D. Single winners chosen by a proportional representation of votes E. Single winners chosen by a simple plurality of votes