The series has two alphabetic series. The first one has CDEFCH and the 2’nd one has MNOPQRSTUVWX
Therefore technically GUV should come in the blank.
Hence option D is the correct one.

Since the letters of the series are same, only the number series is changing perpetually with 3, 4, 5, 6 … and so on, following each letter in an orderly manner. Hence PQR5 Shall come in the blank.
Therefore Option A is the correct one.

The second and forth letters in the series, B and C, are stagnant. However the first and the third letters are changing in a set pattern.

Since the first letters follow a particular order with one letter missed amid each section: L, N, P, T, V. However the second and the third letters are constant but follow a particular direction with a bounced letter: N, P, R, T, V, X.
Therefore Option A is the correct one.

The next alphabet will be V as the series has 5th alphabet from the last one, and the number will be 798 as the differences between two consecutive numbers is a cube. The next number will be 73 = 343 + 455 = 798. Therefore, the next term will be V798.

The middle letters are following the order CDEFGH. The first letters are beginning with P followed by QRSTU. The third letter is beginning with F followed by GHIJK.
Therefore QDG will come in the blank.
Hence Option A is the correct one.

This particular series is following a simple alphabetical order with the first two letters of all segments: C, D, E, F, G, H, I, J, K. Although the third letter is a replicate of the first letter. Hence IJI shall come in the blank.
Hence Option A is the correct one.

The first two letters, AB, are Constant. The third letter is in a particular alphabetic direction, starting with C and the number series is following a descending order starting with 5.

This series the second letter is constant. The first and the third letters are in alphabetical order, beginning with E and F Respectively. Therefore IPJ shall come in the blank.
Hence Option B is the correct one.

The first letters follow the direction ABCDE. The second and third letters are alphabetical beginning with J. The third letter is following the series beginning with P.
Therefore FOU will come in the blank.
Hence option A is the correct one.