The answer is C.
I got this answer by the process of elimination. Not A - Because it is a holy book consisting of the words of God (or Allah) that were revealed to Muhammad in a cave. Not B- The Quran is known for being written in only one language--that's Arabic (translations may be done in different languages, but a Quran itself will always be in the Arabic language.) Not D - Muslims constantly follow the Quran because it is their holy book, much like a Christian with the Bible or a Jew with the Torah.
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