Join ICO's but not the Scammy ICO'S,You can gain a huge profit from joining ICO's And the other 2 choices is good too.You can take all of them you can gain a better and huge profit.
Airdrop is a Form that has a small task given by the developer to Spreadout the name of the token and to know their project. Who fill-up the Airdrop form will be given a token.
To join Airdrops Find some Form to fill-up here's the thread where you can find some Airdrop https://bitcointalk.org/index.php?board=240.0 and fill-up all the requirements given by the developer. Create Facebook Twitter and telegram account that is usefull requirements.
Hold or sell? I will suggest to you to hold now. the reason why all altcoins and bitcoin is down because of Korea Ban the crypto currency in their country.