Final answer:
A 'fleckerl' is a spinning move performed in ballroom dancing, specifically in the Viennese Waltz. Engaging in ballroom dancing can increase one's agility and potentially lengthen life span due to its physical and mental health benefits.
Step-by-step explanation:
The activity in which you might perform a 'fleckerl' is A. Ballroom dancing. This term refers to a spinning step that is typically associated with the Viennese Waltz. Ballroom dancing, aside from being an elegant and traditional form of dance, has numerous health benefits. Studies have highlighted that engaging in ballroom dancing can increase agility and lengthen life span. It involves both physical and mental activity, improving flexibility, balance, and cardiovascular health, while also offering social benefits and the joy of moving to music.