Many people agree that knowledge of English is a must in international trade today.A. th

问题补充：

Many people agree that knowledge of English is a must in international trade today.

A. the, an

B. a, 不填

C. the, the

D. 不填, the

答案：

A. the, an

(答案→)B. a, 不填

C. the, the

D. 不填, the

解析：knowledge 虽为不可数名词，但其前却可用不定冠词，表示某种程度的知识，有类似some的意思；第二空不填冠词，是因为trade 为不可数名词，表示泛指时不用冠词。