'Cause Karma Is My Girlfriend
Riddle: Karma is the most popular girl at her school. At the school's ball, four guys claim to be Karma's boyfriend. Keeping in mind that only the boyfriend tells the truth, can you guess who the boyfriend is if these are the four statements from the guys? 1) Guy #4 is the boyfriend. 2) I am the boyfriend. 3) Guy #1 is the boyfriend. 4) I am the boyfriend.
Answer: Guy #2 is the boyfriend. Only the boyfriend tells the truth, so he will say, "I am the boyfriend,"; therefore, either the second guy or the fourth guy is Karma's boyfriend. If the fourth guy was the boyfriend, then both he and the first guy would be telling the truth, which is against the conditions. Therefore, Guy #2 is Karma's boyfriend.
Source: https://www.riddles.com/index.php/11468
