More than five thousand years ago, Chinese scholars accurately described the flow of blood as a continuous circle controlled by the heart, but it went unnoticed in the West.
(A) but it went
(B) but it was
(C) although it was
(D) but the discovery went
(E) although the discovery was
D is better or E?
D should be better.
Although is not correct usage in this context.
Let me know if i should explain in detail
E changes the intended meaning of the original sentence...
orginal meaning: chinese scholars discovered something great , but it went unnoticed.
E means: chinese scholars discovered something great, although it was unnoticed.
thus, E changes the meaning and is not correct.
think of although as closely meaning "even though" or " inspite of".
i hope this helps. Do let me know if you have more questions.