Lewin's research concerning both how to promote economical and nutritious eating habits, and what kinds of leaders elicit the best work from group members, was important in establishing the idea that
a. different topics require different research strategies.
b. early theories in social psychology were often historically and culturally limited
c. social psychology could be used to understand and help solve practical problems
d. social psychologists may unwittingly influence the behavior of research participants.

The correct option is C: social psychology could be used to understand and help solve practical problems

Explanation:

Lewin was dedicated to researches that aimed to prove that it was possible to study complex social processes scientifically. Thus, he began researches to test various social psychological hypothesis scientifically. He wanted to prove that it is possible to use social psychology in solving practical problems. In this light he conducted a research on how to promote economical and nutritious eating habits, and what kinds of leaders elicit the best work from group members.

C

Explanation:

Lewin's research concerning both how to promote economical and nutritious eating habits, and what kinds of leaders elicit the best work from group members, was important in establishing the idea that social psychology could be used to understand and help solve practical problems.

Lewin is often recognized as the founder of social psychology and was one of the first to study group dynamics and organizational development.