Untin Berta and Ernst Scharrer established the concept

[Luci]

I understand why A, B and C are wrong. And I also understand that D is parallel and it is correct, is just that it sounded a little bit redundant and wordy to say "in which case" two times... What do you think?

[StaceyKoprince]

The "in which case" is part of the parallelism. I agree it sounds a little awkward, but that's common for right answers on harder questions. Also, there is an error with E.

Remember that "which" indicates a noun modifier and must refer to the noun it is touching. It isn't just the hormones which made them endocrine cells - it's the fact that the cells secreted hormones - that whole clause is what we want to refer to - so we can't just use which here.

[thanghnvn]

Pls, help.
I do not understand "in which case". Dose this phrase refer to the whole previous clause. Pls, give examples.

[RonPurewal]

Pls, help.
I do not understand "in which case". Dose this phrase refer to the whole previous clause.

it does, indeed, refer to the whole preceding clause.

you can find a ton of good examples yourself, by typing "in which case" (including the quotes) into google, skipping past the first few pages of hits, and then reading the specific uses that follow.