Who mostly lived in tenement houses during the nineteenth and twentieth century?
a. middle class
b. upper class
c. lower class

d. aristocracy

The correct answer is letter A.

Explanation: In the nineteenth and in the twentieth century most of people classified as middles class were living in tenement houses with bad conditions, but it was where they could live.

me on my last question.

the correct answer is:   the domino theory states that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.