iodine, iron, nickel helium, carbon, gold sodium, chromium, copper phosphorus, nitrogen, oxygen
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which set of elements contains only metals?
Possibilities:
- iodine, iron, nickel
- helium, carbon, gold
- sodium, chromium, copper
- phosphorus, nitrogen, oxygen

sodium, chromium, copper