GMAT Sentence Correction (SC) | Re: In his experiments with gravity, Isaac Newton showed how the

Hichetan2u ,

I am not able to understand"each" vs"each of which"
as you said"each of which " behaves like a subject and hence we need a verb for it.
According to the only difference I see between "each" and "each o which" is the later is wordy.

Just for future reference can I say --> If I come across "each of which" then I shouldalways look for a verb..??

Please assist.