Final answer:
The standard theatre throughout Europe and the United States from the eighteenth century to the early twentieth century was the formal arena stage.
Step-by-step explanation:
The standard theatre throughout Europe and the United States from the eighteenth century to the early twentieth century was the formal arena stage.
During this time period, there were many theatres that were designed with a formal arena stage. These theatres had a separated audience from the stage, comfortable seating for different social classes, and machinery for seamless scene changes. The arena stage became a popular choice because it allowed for a more dynamic staging, although it had limitations in terms of scene changes and blocking the audience's view.