Answer:
The two practices that were more used to develop monopolis are:
d) driving out all business competitors and charging tariffs for crossing state lines.
Step-by-step explanation:
Building a monopoly is illegal in many countries, however, certain strategies worked to establish them without breaking major rules. Driving out all business competitors was the most common technique, the tools that were used were the cost of goods and aggressive prices. However, illegal moves against the business were also performed. The second strategy was charging tariffs for crossing state lines, this still prevails we call them importation taxes and are applied to foreign goods to protect the local producers and help them develop.