To solve this problem, we need to understand the pattern used to encode the word 'ZERO' as 'ADSN'.

Let's break down the encoding:

1. Z to A: The letter 'Z' is the 26th letter of the alphabet, and 'A' is the 1st letter. The transformation here is from 26 to 1, which is a shift of -25.
2. E to D: The letter 'E' is the 5th letter, and 'D' is the 4th letter. The transformation here is from 5 to 4, which is a shift of -1.
3. R to S: The letter 'R' is the 18th letter, and 'S' is the 19th letter. The transformation here is from 18 to 19, which is a shift of +1.
4. O to N: The letter 'O' is the 15th letter, and 'N' is the 14th letter. The transformation here is from 15 to 14, which is a shift of -1.

Now, let's apply the same pattern to encode 'STOP':

1. S: The letter 'S' is the 19th letter. Applying the same shift as 'Z to A' (-25), we get 19 - 25 = -6. Since there are 26 letters in the alphabet, we add 26 to -6, resulting in 20, which corresponds to 'T'.
2. T: The letter 'T' is the 20th letter. Applying the same shift as 'E to D' (-1), we get 20 - 1 = 19, which corresponds to 'S'.
3. O: The letter 'O' is the 15th letter. Applying the same shift as 'R to S' (+1), we get 15 + 1 = 16, which corresponds to 'P'.
4. P: The letter 'P' is the 16th letter. Applying the same shift as 'O to N' (-1), we get 16 - 1 = 15, which corresponds to 'O'.

Thus, the encoded word for 'STOP' is 'TSOP'.

Therefore, the correct option is C.