To the best of my knowledge it's A
Eight presidents have died in office.
These presidents include William Harrison (illness), Abraham Lincoln (assassination), Zachary Taylor (illness), James Garfield (assassination), Warren Harding (illness), William McKinley (assassination), Franklin Roosevelt (illness), and John F. Kennedy (assassination).
Presidency of John Quincy Adams - Wikipedia.
You could check in that.
The killing of four students at Kent University.