问题补充：
The most important thing about cotton in history is part that it played in Industrial Revolution.
A. 不填；不填
B. the; 不填
C. the; the
D. a; the
答案：
A. 不填；不填
B. the; 不填
(答案→)C. the; the
D. a; the
解析：part是先行词被定语从句修饰，是特指；后一空是由普通名词构成的专有名词,特指18世纪后半叶英国工业革命，故两空都选定冠词。
