The following graph shows the results of students in a school.

In which years is the difference in number of students who passed to those who failed maximum?

1993 - 94

Difference in passed to failed students in 1991 - 1992 = 150 - 100 = 50

Difference in passed to failed students in 1992 - 1993 = 200 - 100 = 100 

Difference in passed to failed students in 1993 - 1994 = 300 - 50 = 250

Difference in passed to failed students in 1994 - 1995 = 250 - 100 = 150

Difference in passed to failed students in 1995 - 1996 = 300 - 100 = 200 

Difference is maximum in 1993 - 1994