47.改变平原上的野生动物

change the while wildlife of the plains

46.切掉皮cut off the skins

45.在平原上修建铁路

build railways across the plains

44.用这种种方法　 in this way

43.与土著首领达成协议

make agreements with Native American chiefs

42.抵制做　 resist doing

41.被迫做　 be forced to do

40.向西迁移　 move westwards

39.从1830年起from about 1830 onwards

38.被除数用制成项链

be used to make necklace