Final answer:
Jerry aspires to emulate the swimming abilities of the older boys, reflecting a common theme in coming-of-age stories where younger characters seek to gain recognition and independence.
Step-by-step explanation:
The activity of the older boys that Jerry strives to emulate is d) Swimming. In literature, characters often look up to and try to imitate those they admire, which can be a significant theme in coming-of-age stories. In this context, Jerry is observing the older boys and their displays of skill and autonomy through the activity of swimming. This emulation is reflective of his desire to grow up and be seen as capable and independent, common traits that characters seek to acquire in these narratives.