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.
Comments
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.
Visitors have the option to register a user account, which eliminates the spam filters.