The question asks which attributes are strengths in a teacher's professional role, so each must be judged by whether it improves teaching.

Statement (b) is a strength. Students learn a great deal from what a teacher does rather than merely from what is said, so a teacher who sets examples of punctuality, honesty, fairness and intellectual curiosity teaches those qualities more effectively than any lecture about them could.

Statement (c) is a strength. Willingness to put one's assumptions to the test is the mark of a reflective practitioner: the teacher who asks whether a method is actually working, and is prepared to find that it is not, keeps improving, while one who never questions their assumptions repeats the same mistakes for a career.

Statement (d) is a strength. Acknowledging mistakes builds credibility rather than undermining it, and it models intellectual honesty for students, showing them that error is a normal part of learning rather than something to hide.

Statement (a) is not a strength in this sense. Full-time active involvement in institutional management would take the teacher away from teaching and from students. Administration is a legitimate function, but a teacher fully occupied with it has less time for preparation, instruction and individual attention, so it competes with the core role rather than strengthening it.

Hence the great strengths of a teacher are (b), (c) and (d).