Before____of synthetic（合成的） dyes（染料）, yarns were often colored by

Before____of synthetic（合成的） dyes（染料）, yarns were often colored by dyes obtained from natural vegetable and
　　mineral matter.
　　(A) introducing
　　(B) introduction
　　(C) the introduction
　　(D) introducing that

答案：C 　　测试点：名词／冠词。分析：of 前应为名词，而名词前应有冠词，故选(C).

回答的不错