What is the common factor found in the four U.S. presidents: Abraham Lincoln, James A. Garfield, William McKinley, and John F. Kennedy?

A) Reformed U.S. Army

B) Had blood relation

C) Action against slavery

D) All four were assassinated

Answer: D

Explanation: Lincoln, Garfield, McKinley and Kennedy all share one thing in common: they were assassinated while serving as US presidents.