What was the period in which new territory was acquired known as?

(a)expansion
(b)industrialization
(c)urbanization

The term “iron curtain” was based on an actual iron curtain that german theaters used to separate the stage from the audience in case of a fire. who or what did the “iron curtain” of the cold war separate? democratic nations from communist nations the soviet union from its allies the united states from europe europe from asia

Which of the presidents major role does this passage demonstrate

Are people more motivated to change from positive or negative experiences, like slavery, womens rights, and any other historical movements/moments? i need factual information, not opinions.