It is the correct coding because all the letters are coded by their opposite letters.

Code for L = KM, O = NP, A = ZB, D = CE

G (7^th position from start A) = T (7^th position from back, i.e. Z) W (23^rd position from A) = D (23^rd position from Z) S (19^th position from A) = H (19^th position from Z) Similarly, MQR will be coded as NJI. This option is correct.

It is the correct coding because codes for C is 2; O is 5; N is 7; D is 6; I is 1 and T is 3.

It is the correct coding because the code for G is H, R is T, U is X, M is Q, P is U and Y is E. The coding is done in an ascending order from first to sixth with +1, +2, +3, +4, +5 sequence, respectively.

It is the correct coding because APPEAR should be coded as 688965.

It is the correct coding because TWLIGHT should be coded as GDORTSG. Here, the code of T is G because G is 7^th letter from starting and T is 7^th letter from end. Similarly, W is of D; L is of O; I is of R; G is of T; H is of S; and T is of G.

The place values for all letters in the English alphabet are added in ACID. A = 1, C = 3, I = 9, D = 4; 1 + 3 + 9 + 4 = 17 = 1 + 7 = 8

It is the correct coding because codes of R = &, E = !, T = @, U = %, N = $.

The coding is correct because ATTI is coded as ITTA and TUDE is coded as EDUT.

It is the correct coding because first and last letters are coded by their predecessors and all the letters between first and last are coded by their successors.

It is the correct coding because the coding is done according to place value. 

It is the correct coding because the place value of all the letters are added. Here, place value G = 7, R = 18, E = 5, A = 1, T = 20. Now, when we will add all these numbers, i.e. 7 + 18 + 5 + 1 + 20 = 51.

It is the correct coding because the coding is done alternatively with order +1, 0, so it is the correct coding.

It is the correct coding because the 1^st letter is coded by the code of the sixth letter, 2^nd letter is coded by the code of the fifth letter and so on. Here, the code of C is D; O is N; W is X; B is C and Y is Z.

It is the correct coding because coding is done according to the place values of letters in the english alphabets series. So, the place value of D is 4; E is 5; C is 3; N is 14 and T is 20.

It is the correct coding because all letters are coded alternatively with +1, 0 sequence.

It is the correct coding because the letters are coded by the numbers which are twice their place values.

It is the correct coding because the first letter is replaced by the seventh letter and the second letter is replaced by sixth letter and so on.

It is the correct coding because the codes are: D = &, E = !, V = @, I = $, C = %.