I believe I've heard <<που>> used as a stand-in for "that" or "which" -- is "Τα μήλα που είμαι πράσινα" completely wrong though? (I can change my habit of using <<που>> if so!)
If you typed as you have above..."Τα μηλα που ειμαι"...should be "Τα μηλα που ειναι...Then it would be correct.
2 of the three options are excally the same. I chose one of the 2 correct answers and it was wrong