The structure of this passage could be BEST described in what way?

The passage begins by introducing swimming, narrowing it down to competitive sports and then expanding the concept to figure out what swimming will turn into in the future. Choice "An activity narrowed to a specific purpose and expanded to consider future implications." and choice "An activity narrowed to a specific purpose and expanded to consider future deviations." are close in meaning, but choice "An activity narrowed to a specific purpose and expanded to consider future implications." refers to implications, or effects, rather than deviations, or different versions resulting from changes. This minor change separates the two choices and makes "An activity narrowed to a specific purpose and expanded to consider future deviations." superior. Choice "An activity and its purposes are explained." is relevant, but it does not include the entire scope of the passage. Choice "A supposition regarding the prospect of an activity, analyzed for viability." only focuses on the conclusion and stretches beyond what the passage actually accomplishes.