Good article for the beginners. Bounties are work even today. But airdrops are completely useless now. many of airdrops are a very small value or just a token or a fake. Airdrops were great before the mid of 2018. many people got quite a big profit from those airdrops. I don't know much about the crowd-holding. need to do some research on it. another useless thing is Faucets. It gives you very very less profit. bounties still much profitable than them. in my opinion in Bounties and work for crypto is the best options remain for free earnings.