To keep profis high, factory owners.
To keep profits high, factory owners:
A. Paid top dollar for skilled workers.
B. Kept workers on rigid schedules.
C. Hired only adult men.
D. All of the choices are correct.

The correct answer is "kept workers on rigid schedules". During Industrial Revolution when the rights of the workers were not established yet, factory owners used to abuse of their power by giving rigid schedules to their workers. The other options are incorrect since factory owners not used to give high payments and even used to hire child workers in order to reduce the salaries costs.

Hope it helps!

protectionism fosters competition and keeps price regulated is not an argument in favor of protectionism.