Series Completion

The letters B, C, E, G, and K are the letters in prime value positions. Hence, the next letter is M.
The second letter in each group forms an opposite pair of the first letter in that group. Hence, the next pair in the series is MN.

• The first letters in all the pairs, i.e., A, B, C, and D, form a series of consecutive letters.
• The second letters P, Q, R, and S form another pair of consecutive letters. Hence, The next pair in the series is ET.

• Pattern for the first letter:
  K + 1, L + 1, M + 1, N + 1, O
• Pattern for the second letter:
  P – 1, O – 1, N – 1, M – 1, L
• Pattern for the third letter:
  D + 1, E + 1, F + 1, G + 1, H
• Hence, the next group in the series is OLH.

The alternate groups are in mixed series.
QLR, RNU, SPX are in one series.

• The Pattern for the first letter:
  Q + 1, R + 1, S + 1, T
• The Pattern for the second letter:
  L + 2, N + 2, P + 2, R
• The Pattern for the third letter:
  R + 3, U + 3, X + 3, A

Hence, the next group in the series is TRA.

The given series is a mixed series.

• Pattern for the first letter:
  G – 4, C – 4, Y – 4, U – 4, Q
• Pattern for the second letter:
  T + 5, Y + 5, D + 5, I + 5, N
• Pattern for the third letter:
  B – 6, V – 6, P – 6, J – 6, D

Hence, the missing group is UIJ.

• In each term the numbers are pairs of consecutive prime numbers.
• The letter between them has the place value equal to the product of the two numbers on either side of it.