EXAMPLE : apprentice jewelers ...

After a few weeks’ experience, apprentice jewelers can usually begin to discriminate, though not with absolute certainty, genuine diamonds from imitation diamonds. 
(A) genuine diamonds from imitation diamonds 
(C) between genuine diamonds and imitation diamonds 

(A) genuine diamonds [ DO ] from imitation diamonds 

(C) between genuine diamonds and imitation diamonds [ Prepositional Phrase ]

DO so far from VERB [ discriminate ] is not preferred.

* i've also never seen a modifier stuck directly between a VERB and that verb's DIRECT OBJECT, as in (a) and (b); that is just ridiculously awkward. (c) fixes this problem because there's no direct object; the modifier is inserted before a prepositional phrase. that's common practice. 

Notes:

tips-verb-and-its-direct-object-should