OG11-107,求教

overmatch

In his research paper, Dr. Frosh, medical director of the PWC, distinguishes mood swings, which may be violent without their being grounded in mental disease, from genuine manic-depressive psychosis.
C.between mood swings, which may be violent without being grounded in mental disease, and genuine manic-depressive psychosis

后面OG的解释说"distinguish A from B"是不对的，只有"distinguish between A and B".而且说their应该被省略。
请教：disntinguish A from B为什么不对？字典里面也查得到啊。然后为什么their一定要去掉？

foreverdr

厄。我不成熟的见解。
distinguish A from B 是从B中辨别出了A
而distinguish between A and B 是 区分A和B
根据句意 在他的paper里 他只能区分出了A和B(告知读者两者的区别）并不能在他的paper中由B辨别出了A。
而their必须去掉 我觉得加上很累赘不是麽。如果加上　那麽这个their指的是什麽呢？
hope this helps. : )

loverwy

A答案主要错在"without their being grounded". 在 Gmat里，

介词+one's + doing / 介词+one's +being done 肯定都是错的。