Final answer:
According to the principle of regularity, one should practice or participate in an activity consistently and regularly to achieve the best results, aligning with answer B) Regularly.
Step-by-step explanation:
The principle of regularity refers to the concept that practicing or engaging in an activity on a consistent and regular basis is important for achieving the desired outcome or benefits. When it comes to practicing or participating in events, doing so regularly rather than sporadically increases efficacy and contributes to better results.
In the context of Javier's volunteering schedule, since the choice is to describe how often one should practice according to the principle of regularity, the best answer to the question "The principle of regularity means you must practice:" is B) Regularly. This answer aligns with the concept that consistent participation leads to skill improvement, habit formation, and reaching goals.
Comparatively, practicing sporadically, or only when you feel like it, does not provide the same consistent reinforcement or learning opportunities that regular practice does. Moreover, doing something once a month is also not enough to be considered regular practice, which typically suggests more frequent activity.