OG11-15

(A)
            

(B)and had supplemented

(C)and even though they supplemented

(D)although they supplemented

(E)but with supplementing

OG11说： The logic of the sentence also argues against a construction
that would set the two clauses and the importance of their content
equal when they clearly should not be. The best solution is to have the
main clause describe the primary activity, and a subordinate clause,
although they supplemented, describe the supplementary activity. 如果只看这段的话是不是说，分词就让两个clause的重要性相等了呢？谢谢