Which of the following best describes the term obsessive?

The term "obsessive" is best described as being overly preoccupied, which means having an excessive fixation or concern about a particular thought, idea, or activity. This definition emphasizes the intense focus and often compulsive nature of such preoccupations, which can interfere with daily life and well-being.

In contrast, being very careful or attentive to details pertains more to diligence or meticulousness, which does not capture the compulsive aspect of obsession. Ordinary or commonplace refers to something that lacks uniqueness or significance, which is not related to the intense fixation characteristic of obsessive behavior. Living in seclusion relates to a lifestyle choice of isolation, which also does not connect with the idea of being preoccupied with specific thoughts or actions. Therefore, the term "obsessive," with its connotation of excessive preoccupation, aligns perfectly with the correct choice.