To maintain effective levels of competition in as many markets as possible, the government enforces .

The correct answer is antitrust laws.

Explanation:

Often referred to as competition laws, antitrust laws are statutes enacted by the U.S. government to protect customers from abusive business practices. These laws ensure that in an open-market economy there is fair competition. Along with the economy, these laws have evolved, protecting it against prospective monopolies and threats to the productive ebb and competition stream.

what are the options?

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )