12. what did they call single family homes for working - class families?

Due to Tenements they call single family homes for working.

Explanation:

As more and more people crowded America, single family dwellings were converted into multiple living spaces to increase the space and accommodate the population that was growing day by day.

The tenements were narrow and has less space inside them with improper water system and ventilation. They were also poorly lit and cramped and also lacked plumbing.

The spectators even started building new tenements using cheap materials and shortcuts which was eventually uncomfortable and unsafe. By the end of the 19th century, many people started residing in the tenements, especially in New York which has the most number of them.

d) the constitution rights of native americans and their right to self-government on reservations

porter is writing economic history because he is focusing on the cost of developing vaccines.