Which of the following is classified as an "immoveable obstruction" in golf?

An immoveable obstruction in golf refers to any object that is not part of the course but interferes with a player's stance or swing and cannot be moved. The correct answer, a bridge over a stream, fits this definition perfectly. Bridges are constructed objects that, once placed, cannot be easily moved and serve a specific function on the course. They typically provide players with the ability to cross hazards like streams or ditches, and if they interfere with play, players have relief options according to the rules.

In contrast, other choices do not meet the criteria for immoveable obstructions. Tee-markers are movable as they can be repositioned for each hole. A tree indicating 150 yards is considered a boundary or a natural element of the course and does not qualify as an obstruction in the same way. An out of bounds stake indicates the limits of the course and is not classified as an obstruction either. Understanding the distinction between these categories will help players navigate rules regarding obstructions effectively.