一 语法问题

bnbf

23、Although the Earth's chemical composition had been studied for years, only
toward the end of the nineteenth century _____ as a discipline in its own right.
(A) when geochemistry was recognized
(B) was recognized as geochemistry
(C) then recognized as geochemistry
(D) as geochemistry was recognized
答案是b
实在不明白，哪位能帮忙分析一下这个倒装怎么回事

★vivien★

这是一个让步状语从句,由although引导，the Earth's chemical composition是整个句子的主语部分，在后面的主句中缺少谓语部分因此选B