N is larger than the number 6: Therefore option (D) is disqualified.
N is a factor of 36: The factors of 36 = 1, 2, 3, 4, 6, 9, 12, 18, 36
N is a factor of 48: The factors of 48 = 1, 2, 3, 4, 6, 8, 12, 16, 24, 48
The only answer matching all of the above criteria is Option (A) 12