An Elections Officer Wants to Model Voter Turnout (Y) in a Precinct

An elections officer wants to model voter turnout (y) in a precinct as a function of the type of precinct. Consider the model relating mean voter turnout, E(y), to precinct type: $$E ( y ) = \beta _ { 0 } + \beta _ { 1 } x _ { 1 } + \beta _ { 2 } x _ { 2 } , \text { where } \quad \begin{array} { l } x _ { 1 } = 1 \text { if urban, } 0 \text { if not } \\x _ { 2 } = 1 \text { if suburban, } 0 \text { if not } \\\\\text { (Base level = rural) }\end{array}$$
Interpret the value of $\beta _ { 2 }$ .
A) the difference between the mean voter turnout for suburban and rural precincts
B) the rate of increase in voter turnout $( y )$ for suburban precincts, i.e., the slope of the $y - x _ { 2 }$ line
C) the mean voter turnout for suburban precincts
D) the difference between the mean voter turnout for suburban and urban precincts