Which of the following elements aligns most closely with Adam Smith's vision of capitalism?

A. Marketplace competition to determine prices

B. Economic equality based on socialism

C. Job security provided by strong labor unions

D. Government regulation to protect workers

Marketplace competition to determine price is the one that aligns most closely with Adam Smith's vision of capitalism. The correct option among all the options that are given in the question is the first option or option "A". He was also not in favor of the government mediating in the affairs of privately owned companies.