Answer:
B. Governments at all levels helped business through favorable laws and subsidies.
Explanation:
Government policies contributed to the boom in big business by providing favorable laws and subsidies that supported business growth and expansion. Additionally, while the theory of laissez-faire and minimal regulation (option A) did play a role, it was not the sole factor. Higher tariffs (option C) may have protected domestic industries from foreign competition, but they were not the primary driver of the boom in big business. Therefore, option D is incorrect.