Why is studying demography important on a provincial level? National level?

Data from the 2010 census indicates that China has entered a new demographic era. China’s population grew at a pace significantly slower than that had been anticipated by the Chinese government, averaging 5.7 per thousand over the 10-year period since the 2000 census, significantly below the 8–9 per thousand in the official projections for the same time period.3 Such a growth rate was also drastically lower than that in the preceding two decades, when it was 14.4 and 11.0. This slower growth rate was primary a result of steady low fertility. Meanwhile, urbanization and geographic redistribution happened at an astonishing speed – population in urban centers like Shanghai and Beijing grew as much as 40 percent in one decade, whereas six inland provinces recorded negative population growth for the first time since the end of the Great Leap Forward famine. The census also shows that China’s population has undergone rapid aging – population aged 60 and above accounted for 13.3 percent of the total population in 2010, up by 2.9 percentage points as compared with that from the 2000 census. All in all, the demographic situation in China is vastly different from the decade before.

Explanation:

option d is correct moon- Earth- sun