An option to consider is, Persia.
A. prove the legitimacy of dynastic rule is your answer
Mandate of Heaven was the saying that there should only be one ruler, which the gods approve of. This would rule out B) and D). Because the ruler is approved by the gods, it means that all should obey the appointed king.
hope this helps
I believe that it would be the second option.
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Answer: a stretch of muddy land left uncovered at low tide.
Explanation: