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TF阅读真题第759篇Trade and Early State Formation
Bartering was a basic trade mechanism for many thousands of years; often sporadic and usually based on notions of reciprocity, it involved the mutual exchange of commoditi...
TF阅读真题第760篇Bird Molt
Molt is the process in which birds shed feathers and replace them by growing new ones. It is a costly effort that typically follows breeding in the warmest months of the year and p...
