Erm, I know, er, let's do the Latin declension song.
明白了 我们来唱拉丁变格歌。
It was natural, therefore, that the sovereigns of those countries should be particularly attentive to the interests of agriculture, upon the prosperity or declension of which immediately depended the yearly increase or diminution of their own revenue.
因此,这些国家的君主很自然地应该特别关注农业的利益,农业的繁荣或衰退直接取决于们每年收入的增加或减少。