whiCh oF thE Following ExAmplEs BEst rEFlECts A Cost to soCiEty As DEFinED in thE pAssAgE
A．A FAmily Buying A Dog.
B．EAting in A rEstAurAnt instEAD oF At homE.
C．using lAnD For A housE instEAD oF A pArk.
D．stAying At homE instEAD oF going to sChool.