The Diary of Anne Frank tells the true story of a young girl

[ghong14]

The Diary of Anne Frank tells the true story of a young girl and her family that were hidden during the Nazi occupation of the Netherlands by a gentile Dutch couple, though they were eventually discovered.
a) that were hidden during the Nazi occupation of the Netherlands by a gentile Dutch couple, though they were eventually discovered
b) that were hidden by a gentile Dutch couple during the Nazi occupation of the Netherlands, though they were eventually discovered
c) whom a gentile Dutch couple hid during the Nazi occupation of the Netherlands but were eventually discovered
d) who were hidden by a gentile Dutch couple during the Nazi occupation of the Netherlands but were eventually discovered
e) who were hidden by a gentile Dutch couple during the Nazi occupation of the Netherlands even though they were eventually discovered

Can anyone please explain with WHOM in answer choice C is incorrect? In addition what is a quick test to see when WHOM vs. WHO is appropriate as the modifier.

[tim]

there is nothing wrong with "whom" on its own here. the problem comes from the parallelism issue, and "whom" prevents the two relevant parts from being parallel. please reread the official explanation on this one, because it addresses everything you need to know..