Based on samples drawn from the corresponding populations, in which of the following scenarios will conducting a two-proportion $z$-test be the most appropriate?

A. To compare the proportions of low-income families between British Columbia and Ontario.
B. To compare the mean annual income of British Columbians with a known national mean.
C. To compare the proportion of low-income families with that of high-income families in British Columbia.
D. To compare the mean annual income of male British Columbians with that of female British Columbians.
E. To compare the proportion of low-income families in British Columbia with a known national proportion.