The correct answer is C. N.

The missing character is the one that completes the following pattern:

  • The first letter of each month of the year is followed by the number of days in that month.
  • The letters are in alphabetical order.
  • The numbers are in ascending order.

The first letter of each month of the year is:

  • January: J
  • February: F
  • March: M
  • April: A
  • May: M
  • June: J
  • July: J
  • August: A
  • September: S
  • October: O
  • November: N
  • December: D

The number of days in each month is:

  • January: 31
  • February: 28 (29 in leap years)
  • March: 31
  • April: 30
  • May: 31
  • June: 30
  • July: 31
  • August: 31
  • September: 30
  • October: 31
  • November: 30
  • December: 31

The letters in alphabetical order are:

  • A
  • B
  • C
  • D
  • E
  • F
  • G
  • H
  • I
  • J
  • K
  • L
  • M
  • N
  • O
  • P
  • Q
  • R
  • S
  • T
  • U
  • V
  • W
  • X
  • Y
  • Z

The numbers in ascending order are:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

The only letter that is not in the pattern is N.