The correct answer is A) Clarity or understanding, enlightenment.
The other options of the question were B) Casting a shadow of a doubt. C) To feel ill suddenly. D) a nation that experiences an epidemic illness.
The best definition of “illumination” is "Clarity or understanding, enlightenment."
It is a word more often used in religion, spirituality or inspirational topics. Illumination means that the individual has reached a level of knowledge and understanding that makes him/her a peaceful being, tolerant, and compassionate with other fellow beings, capable of understanding different truths.