By the 1840s the influx of p（）to the Northwest， and the flood of prospectors to California after 1848 had created an increasing demand for mail delivery to and from the East.(–the first people to go to a particular area in order to live and work there)?

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正确答案：pioneers

Tag：时间：2023-10-07 15:10:38

上一篇：Later this route was ultimately j（）by growing North-South tension.(–cause sth.to be harmed， lost or destroyed; put in danger)
下一篇：The Pony Express， nevertheless， has become s（）with the Old West.(–having the same， or nearly the same， meaning)?