The best method to inspire students for hard labour is

Concept: Motivation to work can be built through different channels — direct modeling, extrinsic reward, verbal instruction, or vicarious example. Educational psychology holds that the most durable inspiration comes from observational learning: learners adopt a behaviour by watching and imitating a credible, relatable model who demonstrates it in person (Bandura's social learning theory), captured by the maxim "example is better than precept." External rewards, by contrast, tend to tie effort to the incentive and can weaken intrinsic motivation once the reward is withdrawn.

Application: Among the given methods, a teacher who personally does hard work places a live, high-credibility model in front of students every day. Because students observe and imitate the person who guides them, this direct demonstration converts into spontaneous, internalised motivation to work hard — the strongest and most lasting form of inspiration for sustained effort.

Why the other methods are less effective:

• Rewarding hardworking students uses an external incentive; it can raise effort while the reward lasts but ties motivation to the prize rather than to the work, and may reduce intrinsic drive once withdrawn.

• Delivering a lecture on the importance of effort only tells students what to value; exhortation without a lived demonstration seldom converts into sustained behaviour.

• Presenting others' success stories offers a symbolic, second-hand model that is more distant and less relational than a teacher the students meet in person.

Conclusion: Hence the most effective method is for the teacher to demonstrate hard work personally, inspiring students through direct example.