Identify the missing letter to complete the alphabetical series.

B, E, I, N, ?

The correct option is T.

To find the missing letter in the alphabetical series, let us determine the numerical positions of the given letters in the English alphabet:

B = 2

E = 5

I = 9

N = 14

Now, let us examine the pattern of differences between the positions of consecutive letters:

$5-2=3$

$9-5=4$

$14-9=5$

The difference between consecutive positions increases by 1 each time (+3, +4, +5). Following this pattern, the next difference must be +6.

Adding 6 to the position of letter N (14):

$14+6=20$

The 20th letter in the English alphabet is T.

Therefore, the missing letter that completes the series is T.