The next two letters are U and F. Hence, option (4) is the correct answer.

The series consists of writing 3 letters in reverse alphabetical order from both the sides of the English alphabet. Z, Y, X, C, B, A, W, V, U, F, E, D. So, the next letters will be T, S, R. Hence, 2^nd option is right. 

The series follows the order: + 2, + 3, + 2 and + 3

T – 3 = Q Q – 3 = N N – 3 = K K – 3 = H H – 3 = E

The series consists of English alphabet starting from Y onwards (–1, –2, –3, –4 …… Y, W, T, P K, E, X, P, G). So, the right answer is option (1). 

The sequence consists of two series.

Backward series: XYZ, UVW

Forward series: CBA, FED The letters in both the series are arranged in reverse order. Hence, option (1) is the correct answer. 

The series consists of writing one letter and skipping one and writing two letters in the reverse order and again skipping one and so on. Hence, option (1) is the right answer. 

The group consists of 3 series of letters.

The group consists of 3 series starting from D, K and Y. The first series is +2 series, the second series is –1 series and the third series is –2 series. Hence, 3^rd option is correct. 

The group consists of 3 letter series starting with C, J and Q. Each letter in the next term has moved one step forward, i.e. + 1. Hence, option (3) is the right answer. 

It’s a + 5 series. 

There are two series running concurrently, one starting with the first letter of the alphabet (A) and the second with the last (Z). Thereafter, it is +1 at each step for the series starting with A and -1 for the series starting with Z. So, the correct answer is option (1).

The group consists of 3 different series starting with Z, U and A. The first series is – 2, the second series is of vowels starting from the last in english alphabets and the third series is + 2. Hence, option 1 is correct. 

The group consists of 3 different series starting from D, E and B and moving 5 letters forward. Hence, 2^nd option is correct. 

The series moves in + 4, + 5, + 6 and so on.

The group consists of two series starting with B and D, and moving five letters forward.

The first group consists of three different letters and the second group is H + 9, K + 9, N + 9 and so on.

The last group should be Z + 9; C + 9; F + 9

After every 3 letters, one, two and three letters are skipped in each respective pattern. DEF (G) HIJ (KL) MNO (PQR) STU Hence, option (1) is the correct answer. 

This series follows the pattern: + 2, + 4, + 2, + 4   So, the next letter to Q will be U. Hence, option (4) is right. 

The series consists of three different series starting with A, B and Z.