Who has won the most Grand Slams in tennis?

Pete Sampras
Rod Laver
Roger Federer
Rafael Nadal

Correct answer:

Roger Federer (2)

Since the beginning of the open era, five men (Rod Laver, Andre Agassi, Roger Federer, Rafael Nadal, Novak Djokovic) and six women (Margaret Court, Chris Evert, Martina Navratilova, Steffi Graf, Serena Williams and Maria Sharapova) have won Career Grand Slams in singles play.