Among all methods of cannabis oil extraction below , which one is the most efficient? 1) Solvent extraction (using ethanol); 2) Carrier oil extraction (using olive oil); 3) Super- or sub-critical carbon dioxide extraction; and 4) Light hydrocarbon extraction.

Thanks for the question!  This is a pretty common question with a fairly complicated answer, so check out this related question on the Cannabis ECN: https://cannabis.expertcallingnetwork.com/ask/what-are-the-safest-and-the-most-effective-ways-to-extract-and-produce-cbd-rich-cannabis-oil-co2-oil-or-ethanol