Correct Answer: DISTART

Solution : Given:
GEMDISTIONARY

Now, let's compare all the option words with the word GEMDISTIONARY –
First option: GAME; All the letters of GAME are present in the word GEMDISTIONARY.
Second option: STAR; All the letters of STAR are present in the word GEMDISTIONARY.
Third option: MEGASITY; All the letters of MEGASITY are present in the word GEMDISTIONARY.
Fourth option: DISTART; The letter T appears only once in the word GEMDISTIONARY. But, in DISTART, T appears two times. Therefore, all the letters of DISTART are not present in the word GEMDISTIONARY.

So, from the above, only DISTART cannot be formed from the word GEMDISTIONARY. Hence, the fourth option is correct.