Step 1: Identify what kind of answer is needed.
We need the name of a scholar tied to a specific model, the two-step model of attitude change. So the work is to match each name with the idea he is famous for.
Step 2: Match Fritz Heider.
Heider is linked with the balance theory of attitudes, which deals with harmony among a person, another person and an object. No two stages are involved. Option (1) does not fit.
Step 3: Match Leon Festinger.
Festinger is linked with cognitive dissonance, the mental discomfort from conflicting thoughts that pushes a person to change. This is one mechanism, not two steps. Option (2) does not fit.
Step 4: Match S. M. Mohsin.
Mohsin worked on persuasion in the Indian setting. His model says the person first forms a bond with the influencing source, and only then accepts the source's view. That makes two clear steps. Option (3) fits.
Step 5: Match Richard Lapiere.
Lapiere is linked with the well known field study that showed people's words and deeds can differ. It is not a model of attitude change. Option (4) does not fit.
Step 6: Double check the pick.
Only one of the four names is tied to a model with two stages, identification first and acceptance second. The other three names are tied to balance, dissonance and the attitude-behaviour gap, so they cannot be the answer. This leaves Mohsin alone.
Final Answer:
Only Mohsin is tied to the two-step model, so option (3) is right.\[ \boxed{3} \]