First letter in every group is in reverse alphabetical order i.e. SRQPON. The middle letter is in alphabetical order i.e ABCDEF and the last letter has pairs, BB, DD & FF.

The series is xyz/yzx/zxy /xyz/yzx/zxy . So, the letters change places in a cyclic manner.

In this series, the letters remain the same: DEF.

The subscript numbers follow this series:

111, 112, 122, 222, 223, 233, 333, …

X – 3 = U – 2 = S – 1 = R – 1 => Q – 3 = N – 2 = L – 1 = K – 1 => J – 3 = G – 2 = E – 1 = D, ____ =>CZXW

The first letter of each term follows the series J, K, L, M and N. This eliminates choices A, C, and D. Thus, the correct answer is NEO

The first two letters, PQ, are static. The third letter is in alphabetical order, beginning with R. The number series is in descending order beginning with 5.

This series consists of a simple alphabetical order with the first two letters of all segments: B, C, D, E, F, G, H, I, J, K. The third letter of each segment is a repetition of the first letter.

As per the given pattern of letter series in above question ,
B (+3) → E (+3) → H (+3) → K (+3) → N (+3) → Q
After completing the pattern, we will get complete letter series.
BBEEHHKKNNQQ

The given series is a mixed series. The pattern for the first letters:

The given sequence consists of two series :
I.    Z, W, T, V, Q, ? in which each letter is moved three steps backward to obtain the next term.
II.   S, O, K, G in which each letter is moved four steps backward to obtain the next term.

The letter of the word are written in a reverse order and each letter, except the first and the last one, is moved one step forward, to obtain the code

S      U       G       A        R
R     P         K       L         U

From the above, we get

S = R

U = P

G = K

A = L

R = U

Similarly,

G       U     R        U       S
K        P     U        P       R

Z+3=C-2=A+3=D, X+3=A-2=Y+3=B, V+3=Y-2=W+3=Z,_______ T + 3 = W – 2 = U + 3 = X => TWUX

Z-2=X-2=V-1=> U-2=S-2=Q-1 => P-2=N-2=L-1=> K-2 = I-2 = G => KIG

Corresponding numbers of the letters are squared, and taken in alphabetical order.

Hence E = 52 = 25 => Y = EY

BCE, FGI, JKM, NOQ, …..

B+1-C+2-E,+1 => F+1=G+2=I,+1 => J+1=K+2=M,+1 => N+1=O+2=Q,+1 => R+1=S+2 = U

AB, CD, EF, GH are in alphabetical order and YZ, WX, UV are the corresponding letters of the alphabets in reverse order.

AM, BL, CK, DJ, => EI

First letter of the series in alphabetical order

From A Second letter is in reverse alphabetical order from M

In alphabetical order, middle letter is decreasing by 1 letter.

In the first letter of the every series is increasing by 1, middle letter is continuously decreasing by 1 [-1].

Third letter is increasing by [+1], from their previous series.

This series consists of a simple alphabetical order with the first two letters of all segments: B, C, D, E, F, G, H, I, J, K. The third letter of each segment is a repetition of the first letter.

The middle letters are static, so concentrate on the first and third letters. The series involves an alphabetical order with a reversal of the letters. The first letters are in alphabetical order: F, G, H, I , J. The second and fourth segments are reversals of the first and third segments. The missing segment begins with a new letter.

The first, fourth and seventh letters are in alphabetical order. Thus, tenth letter would be after C i.e. D. Also, second and third letters are in reverse order and so are the fifth and sixth letters.

The first letters are in alphabetical order with a letter skipped in between each segment: C, E, G, I, K. The second and third letters are repeated; they are also in order with a skipped letter: M, O, Q, S, U.

The second and forth letters in the series, L and A, are static. The first and third letters consist of an alphabetical order beginning with the letter E.

There are two alphabetical series here. The first series is with the first letters only: STUVW. The second series involves the remaining letters: CD, EF, GH, IJ, KL.

The series is baab / baab / baab / baab / b.
Thus, the pattern baab is repeaated

The series is abc/bca/cab/abc/bca, Thus, the letters change places in a cyclic order.