Answer:
D) by creating monopolies and establishing trusts
Step-by-step explanation:
Monopolies are usually set up in order to eliminate other companies trying to compete with the solely approved company.
This means only one company renders the service and then the returns are always very high and maximal due to zero competition.
This helped them accumulate wealth.
The trust is like a will but it takes effect after it is created unlike the will which takes effect after the individual dies.
A trust helps in the efficient management of one’s property and wealth which also helped the American industrial leaders in the sustenance of the wealth.