Which of the following is an example of a bill of attainder?

A bill of attainder is a legislative act that punishes an individual or group without a trial. In the context of the given options, the correct example describes a situation where the president signs a bill that explicitly makes entering the country illegally a federal crime. This action can be viewed as singling out a specific behavior and applying a penalty directly to those who commit it, which aligns with the concept of a bill of attainder.

The other options do not fit this definition. For example, a bill allowing for trial by jury does not impose punishment without a trial; rather, it guarantees legal rights. Similarly, a bill that increases taxes on imported goods or regulates interstate commerce affects broad categories of behavior and commerce rather than targeting specific individuals for punishment. Thus, option B correctly embodies the characteristics of a bill of attainder by establishing a criminal offense and its associated penalties.