题目内容：

阅读下面材料,在空白处填入适当的内容（1个单词）或括号内单词的正确形式

The USA is a land of immigrants. Between 1815 1. 1914, the world witnessed the greatest peaceful migration in its history: 35 million people, mostly Europeans, left their homelands to start new lives in America. Why did these people risk everything by 2. (leave) their homes and families?

First, what forced emigrants 3. (make) the decision to leave? One major cause for European farmers to leave was the rise in population, 4. in turn led to land hunger. Another was politics. There was an increased taxation and the 5. (grow) of armies, and many young men fled eastern Europe to avoid being forced to join the army.

Physical hunger provided another pressing reason. Following the collapse (衰退) of the economy of southern Italy in the 1860s, hundreds of thousands decided to start a new life in America. Religion also encouraged millions to leave the Old World.

In short, people 6. (choose) to leave their homes for social, economic and 7.(religion) reasons. As a result, by 1890 among a total population of 63 million, there were more than nine million foreign-born 8. (America).

But what were the attractions? First of all, there was the promise of land that was so scarce in Europe. Next, factories were calling for workers, and pay conditions were much better 9. back home. Men 10. (need) to open up the West and build the long railroads, and new towns needed settlers to live in and to develop business. There was the space for people to practice their faith in peace.