In a certain code language, OMNIPRESENT is written as QJONPTSMDRD. How is CREDIBILITY written in that code?

Answer: Option C

Keeping the middle letter as it is, the first five and the last five letters of the word are written in the reverse order. In the group of letters so obtained, the first five letters are each moved one step forward, the middle letter is moved two steps forward and the last five letters are each moved one step backward to get the code.
Thus, we have :
CREDI/B/ILITY => IDERC/B/YTILI => JEFSD/D/XSHKH