What characterizes a "union shop"?

A "union shop" is characterized by the requirement that employees must join the union within a specific timeframe after being hired. This means that while new employees may not need to join immediately upon starting their job, they are obligated to become members of the union within a certain period, which is typically defined in the collective bargaining agreement. This model is designed to ensure that all workers benefit from the union's representation and collective bargaining efforts while also helping maintain strength in numbers for the union.

Other options touch on different aspects of union membership but do not accurately define a "union shop." For example, the first option suggests that employees can choose whether to join the union, which aligns more with an "open shop" model where union membership is not required. The third option implies that only certain positions require union membership, which suggests a selective approach that does not reflect the uniformity of membership obligations found in a union shop. The fourth option alludes to financial responsibilities related to union membership but does not capture the core characteristic of mandatory membership following a hiring period that defines a union shop.