I would invest my bitcoins in studying because with enough money i can buy all the books i want to buy and want to build a career of my own and live a very enoughable and healthy life .
One of the smartest things I have seen in this thread, investing in your knowledge, schools is the best choice that man can make. School can take time and money, poor people need to waive on many things, but that will pay out one day.
If there isnt any profitable and safe investment in the moment, school is the second best choice. That is better then risking your money on some investment where you can lose all your money, knowledge from school stays for the rest of out lives, and that knowledge can bring a lot of money and food on the table.
Knowledge does not stay forever unless you apply it in your daily life. Otherwise, it will vanish and you'll try to remember it and you'll realize that you've already forgotten all of it. Also consider that school is a long term thing. If you only study for a year or for a semester, there wouldn't be that much difference since you still don't have any diploma in you. You could've used that money for other investments.
Only go back to school if you have a lot of time. You should have at least 8 hours of free time to keep up on school works. Don't go to school if you already have a full-time job or if you're too busy because you're just going to end up wasting your money.