When you design solution, you have to decide if you're protecting against targeted or not targeted attack. It's not all just "spam".
If your concern are only dumb, fully-automated bots not targeting your site specifically (which is true for the bottom 99.5% of the web) then you don't need CAPTCHA.
2 and 3 are great for non-targeted attack. 1 is a very weak protection against targeted attack and it's likely an overkill unnecessarily burdening users.
If your concern are only dumb, fully-automated bots not targeting your site specifically (which is true for the bottom 99.5% of the web) then you don't need CAPTCHA.
2 and 3 are great for non-targeted attack. 1 is a very weak protection against targeted attack and it's likely an overkill unnecessarily burdening users.