Explanation:

Here's how we break this one down:

- Take the word "AUTHORISE."

- For every consonant, swap it with the next letter in the alphabet. For vowels, use the letter right before it.

- A (vowel) ? Z

- U (vowel) ? T

- T (consonant) ? U

- H (consonant) ? I

- O (vowel) ? N

- R (consonant) ? S

- I (vowel) ? H

- S (consonant) ? T

- E (vowel) ? D

- So, converted, you get: Z T U I N S H T D

Now, you arrange these from right to left in reverse alphabetical order:

- List the letters, biggest to smallest alphabetically: Z, U, T, T, S, N, I, H, D

- So, from right to left, it becomes: D H I N S T T U Z

- Now, if you count from the left end, the third letter is I.

So, out of your options, the correct answer is:

Option 3: I