The series given is: A, E, I, ?, Q, U
Let's find the position of each letter in the alphabet:
A = 1st position
E = 5th position
I = 9th position
Q = 17th position
U = 21st position
Finding the pattern by examining the differences between consecutive positions:
E - A = 5 - 1 = 4
I - E = 9 - 5 = 4
Q - ? = difference should be 4
U - Q = 21 - 17 = 4
The pattern shows each letter is 4 positions ahead of the previous letter.
To find the missing letter:
I is at position 9
The next letter should be at position: 9 + 4 = 13
The 13th letter of the alphabet is M.
Verification of complete series:
A (1), E (5), I (9), M (13), Q (17), U (21)
All consecutive differences equal 4.
Therefore, the answer is Option 2: M