controversial – adj. relating to or causing much discussion, disagreement, or argument : likely to produce controversy. “Controversy” is the noun of controversial. (“In the U.S. some issues such as gun control are very controversial; so, people argue about them all the time.”
incentive – n. something that encourages a person to do something or to work harder (“If you want your employees to work hard for you, you need to give them the proper incentive!”)
clear-cut – adj. sharply defined; easy to perceive or understand (“The answer is not so clear-cut. The issue is so confused that it is difficult to know who is right and who is wrong.”)