Correct Answer: AMBITION

Solution : Given:
EXAMINATION

Now, let's compare all the option words with the word EXAMINATION –
First option: NATION; All the letters of NATION are present in the word EXAMINATION.
Second option: EXAM; All the letters of EXAM are present in the word EXAMINATION.
Third option: MENTION; All the letters of MENTION are present in the word EXAMINATION.
Fourth option: AMBITION; All the letters of AMBITION are not present in the word EXAMINATION. B is not present in the word EXAMINATION.

So, from the above, only AMBITION cannot be formed using the letters of the word EXAMINATION. Hence, the fourth option is correct.