Explanation

The pattern appears to be the number of letters in each word:

DRIVER has 6 letters, but the value is 7 ( possibly due to a additional constant or a different calculation)

PARLIAMENTARIAN has 15 letters, but the value is 16 (again, possibly due to a additional constant or a different calculation)

If we apply the same pattern to SECRETARY, which has 9 letters, we get:

SECRETARY = 10 (using the same offset as before)

So, the correct answer is: 10

Explanation

The pattern of the sequence appears to be a alternating addition and subtraction of numbers:

14 - 5 = 9

9 - 4 = 5

5 + 16 = 21

21 - 13 = 8

8 + 5 = 13

13 + 15 = 28

28 - 19 = 9

So, the next number in the sequence would be:

9 + 10 = 19

Explanation

The pattern of the sequence appears to be an alternating addition of 9 and 2:

12 + 9 = 21

21 + 2 = 23

23 + 9 = 32

32 + 2 = 34

34 + 9 = 43

So, the missing number is: 43

Explanation

By Decoding the given Sequence in the way $A\to 1;B\to 2;....Z\to 26$

$A,D,H,M,S\to 1,4,8,13,19$

The difference between two successive numbers is increasing by '1' starting from with '3'

$1+3=4$

$4+4=8$

$8+5=13$

$13+6=19$

$19+7=26$

Hence according to decoded language the next number is '26' i.e $Z$

Explanation

The sequence alternates between adding 3 and subtracting 1. Following this pattern:
7 (+3) → 10 (-1) → 9 (+3) → 12 (-1) → 11 (+3) → 14 (-1) → 13.