句式一: 變化主體/圖畫中主體+趨勢動詞+副詞+時間區(qū)間
    Eg: The number of aged people over 65 increased significantly from 1940-2000.
    The number of aged people over 65 dropped slightly from 1960-1980.
    The number of aged people over 65 fluctuated between 1 million and 1.2 million from 1940-1950.
    The number of aged people over 65 remained stable from 1930-1940.
    句式二: There be + 形容詞 + 表示趨勢的名詞 + in+ 變化的主體+ 時間區(qū)間
    Eg: There was a significant increase in the number of aged people over 65 from 1940-2000.
    There was a slight decline in the number of aged people over 65 from 1960-1980.
    There was a fluctuation between 1 million and 1.2 million from 1940-1950.