各位大神，谁来帮忙分析一下这段话（ 主要是This那句) ：
By 2001, the population of the United States will be at least 250 million and possibly 270 million, and the nation will find it difficult to expand food production to fill the additional mouths. This will be particularly true since energy pinch will make it difficult to continue agriculture in the high-energy American fashion that makes it possible to combine few farmers with high yields.
By 2001, the population of the United States will be at least 250 million and possibly 270 million, and the nation will find it difficult to expand food production to fill the additional mouths. This will be particularly true since energy pinch will make it difficult to continue agriculture in the high-energy American fashion that makes it possible to combine few farmers with high yields.
