Which of the Following Is the Primary Reason That the Zhou

Which of the following is the primary reason that the Zhou made efforts to perfect their astronomical system?

A) They were strong believers in astromancy.
B) They needed to be able to date the reigns of Zhou rulers.
C) They needed to provide work for unemployed scholars who might otherwise write satires about the Zhou court.
D) Since the Zhou ruled by the will of the heavens, they needed to create an accurate calendar for agricultural and religious events.