Pensive means engaging or involving deep or serious thoughts.
Option B is the correct answer because “reflective” means relating to or characterized by deep thought; thoughtful. hence it is the correct answer.
Option A is incorrect because “cheerful” means being happy and gleeful which is not related to the given word.
Option C is incorrect because “confused” means being in a state of dilemma or confusion which is not the meaning of the given word.
Option D is incorrect because “depressed” means being upset about something, it is not the correct meaning of the word given.