我们展示了 task 1主体段落的写作，大家可以看到我们对句式的变换和主语的切换：
In the beginning of the 20th century butter was far more preferable in the US, amounting to just over 8 kg compared to only about 1 kg of margarine. The consumptions of both sorts of fat, though, remained relatively constant from 1910 to 1940, the onwards period over the next five-decade shows consumers increasingly turned to margarine peaking at roughly 7 kg, and demand for butter melted away, troughing at 2 kg.
The vegetable-based spread remained dominant for the last two-decades. But two trends have since eaten away at its market share, particularly for margarine. Today the average American consumes just 1.6 kg of the stuff each year, down from over 5 kg per person in the early 1990s.
以上划线句子是主语变换的展示，黑体字是有用的词汇。