Which of the following describes an important difference between the muslim calendar and the gregorian calendar?

a. the gregorian calendar accurately tracks the sun's movements, while the gregorian calendar tracks the moon's movements.
b. the gregorian calendar is divided based on jesus's birth, but the muslim calendar starts when muhammad moved to medina.
c. the muslim calendar describes time as a set of repeating cycles, while the gregorian calendar describes time as a straight line from past to future.

d. the muslim calendar is only used by religious leaders, while the gregorian calendar can be used by any member of a christian society.
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