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

First of all, the pronoun "each" is always singular, so the answers that pair "each" (singular) with "their" (plural) are incorrect. That immediately eliminates (A), (B), and (E).

The problem with (C) is ---- the relative pronoun "which" is supposed to introduce a relative clause, with it's own noun + verb. Instead, in (C), "which" is followed by a participial phrase, "contributing . . ." That's grammatically incorrect. It's also unnecessarily
...

---