quasi- Usually hyphenated when used to form a compound adjective: a quasi-public corporation. When in doubt, consult Merriam-Webster’s.

questionnaire Double n.

question whether, question of whether, question as to whether The first phrasing is the best, the second is next best, and the third is to be avoided.

Quran is the preferred spelling for the Muslim holy book. Use the spelling Koran only if in a specific title or name (AP style).