The total market value of real estate has declined over the past four years .
As a result , assessed value of that real estate has also declined .
The percentage of assessed value that was paid as property taxes to the city has remained the same .

Total property tax collected 4 years ago = Assessed value of real estate 4 years ago* Property tax %
Total property tax collected at present = Assessed value of real estate at present * Property tax %

Pre-thinking: Since the assessed value has declined , the total property tax will decrease .

A. The percentage of Altonville’s yearly revenue that comes from money collected in property taxes did not change over the past four years.
Out of scope - we have no information on percentage of Altonville’s yearly revenue and the amount contributed by property taxes to the total revenue.
B. The percentage of Altonville’s yearly revenue that comes from money collected in property taxes has declined steadily over the past four years.
Might be true - but need not be true - The total Altonville’s yearly revenue might be declined by bigger % .
C. The amount of revenue that Altonville collected from property taxes was lower last year than it was four years ago.
Correct
D. During the past four years, Altonville officials increased tax rates on other sources of revenue such as retail sales and business profits.
Out of scope
E. Altonville will soon require property owners to pay a higher percentage of the assessed value of their property as property tax.
Might be true - but need not be true