Who amongst the following Tennis players has won the most number of Grand Slam titles ?

Leander Paes
Rafael Nadal
Pete Sampras
Andre Agassi

The correct answer is (b), Rafael Nadal. He has won 21 Grand Slam titles, the most of any male player in history.

Leander Paes is an Indian tennis player who has won 18 Grand Slam titles, but all of them in doubles or mixed doubles. Pete Sampras is an American tennis player who has won 14 Grand Slam titles, all in singles. Andre Agassi is an American tennis player who has won 8 Grand Slam titles, 6 in singles and 2 in doubles.