Common characteristics of livable cities are

a$.$ Low population density, heterogeneous mixtures of residences and businesses, wide highways, and abundant parking for efficient transportation.

b$.$ Low population density, concentrated housing, few stores and businesses, wide highways, and abundant parking.

c$.$ high population density but heterogeneous mixtures of residences and businesses that encourage people to socially interact.

d$.$ high population density, concentrated housing, limited business and stores, and a car$-$centered approach that makes driving easy.