Those teachers are popular among students who

Concept — what earns a teacher lasting regard from students

Teaching is a helping profession. Besides delivering content, a teacher carries the professional roles of guide, facilitator, motivator and counsellor, and teacher effectiveness is judged by how far the learner's genuine academic and personal needs are met. Regard from students therefore grows out of the teacher's usefulness to their learning, not out of favours, leniency or informal closeness.

Applying the idea to this item

1. Read each behaviour for what it actually gives the learner, and ask which one serves the learner's own growth.

2. Working through a student's problems meets a real need: the student leaves with the difficulty resolved and better able to learn independently. This is the teacher's professional role of guide and counsellor actually being performed.

3. Lasting popularity follows from that usefulness — students value the teacher they can take a problem to.

Cross-check — why the other behaviours do not explain lasting regard

• Developing intimacy puts friendliness in place of professional guidance; it may win momentary liking, but it removes the distance a teacher needs in order to guide and correct.

• Awarding good grades operates on the mark sheet: a favourable grade is an outcome of assessment rather than an act of teaching, so by itself it explains attachment to the score and not lasting regard for the teacher.

• Taking classes on an extra tuition fee converts the teacher's help into a purchase, and is professionally unethical when it duplicates the teaching already owed to the class.

Therefore the teacher who helps students solve their problems is the one who is popular among them.