The historian Frederick J. Turner wrote in the 1890’s that the agrarian discontent that had been developing steadily in the United States since about 1870 had been precipitated by the closing of the internal frontier——that is,the depletion of available new land needed for further expansion of the American farming system. (4)
解释:典型的句子套句子。主句是F.J.T. wrote that,宾语从句中主干是the agrarian discontent had been precipitated by the closing of the internal frontier,在从句的主语the agrarian discontent后面又来了一个定语从句。
训练:The historian Frederick J. Turner wrote in the 1890’s that the agrarian discontent that had been developing steadily in the United States since about 1870 had been precipitated by the closing of the internal frontier——that is,the depletion of available new land needed for further expansion of the American farming system.