根据文章的意思，在空白处填上一个适当单词

　　They hunted bison, a type of cattle which used to exist 1 huge numbers on the plains of America. The bison grows 2 a shoulder-height of 1.5 metres and can weigh 1,100 kilograms. It was an important part of native Americans' life, Bison 3 killed for their meat, 4 their fur provided warm clothing during cold winters. The native Americans made tents and water containers 5 the skins and tools from the bones. The teeth were used to make necklaces.

　　From about 1830 6 in the USA and from about 1870 in Canada, European settlers began to move westward. Large groups of native Americans were forced to move away from their old hunting grounds. When they resisted, they were killed. There were many fierce wars between native Americans and European settlers. Settlers made agreements 7 native American chiefs but always broke them afterwards. 8 this way; native Americans were forced onto poor land that settlers did not want.

　　The settles built railways 9 the plains and began to hunt even more bison. While early settlers had killed bison 10 food, now the killing became more widespread. They killed the bison, cut off the skins and left the bodies to rot.