Identify and analyze the factors that changed the American city in the 2nd half of the 19th century. ( I need three things to talk about since it's going to be a long essay but I just need help starting it. )

Which of the following was used only once, to ratify the 21st amendment (repealing prohibition)? a. three-fourths of both houses of congress. b. three-fourths of the state legislature approved it. c. two-thirds of the state legislature approved it. d. ratifying conventions in three-fourths of the states approve it.