Which of the following is NOT a personal grooming habit?

The choice of using public transport is not a personal grooming habit because personal grooming specifically refers to activities that individuals engage in to care for their physical appearance and hygiene.

Brushing hair daily, wearing polished shoes, and maintaining nail hygiene are all practices that involve directly enhancing one's appearance and ensuring cleanliness. These activities contribute to a well-groomed personal image, which is important in professional settings. On the other hand, using public transport does not relate to grooming or personal appearance but rather to a mode of transportation and how one chooses to commute. Therefore, this option stands out as the one not associated with grooming habits.