In a certain code 'FAIL is written as IFLA’ and 'SOUL is written as 'USLO’. How is 'DUST' written in that code?

SDTU

Given; In a certain code 'FAIL is written as IFLA’ and 'SOUL is written as 'USLO’.

So,

(The pattern followed here is like the first letter is interchanged with 2nd, 2nd is 4th, 3rd is 1st and 4th is interchanged with 3rd) 

Thus as per the explanation;

 F A I L = I F L A

And,

 S O U L = U S L O

Similarly,

 D U S T = S D T U

Therefore, the correct option is SDTU