Correct Answer: DIRECTION

Solution : Given:
DISSERTATION

Now, let's compare all the option words with the word DISSERTATION –
First option: SISTER; All the letters of SISTER are present in the word DISSERTATION .
Second option: STATION; All the letters of STATION are present in the word DISSERTATION .
Third option: DIRECTION; All the letters of DIRECTION are not present in the word DISSERTATION as C is not present in the given word DISSERTATION.
Fourth option: RATION; All the letters of RATION are present in the word DISSERTATION .

So, from the above, only DIRECTION cannot be formed using the letters of the word DISSERTATION. Hence, the third option is correct.