WordPress Anti-spam Comments Plugin

Spam comments can be annoying sometimes, especially when they are sent by machines. Here are three anti-spam comment plugins, mainly to prevent machines:
1. Clickcha
I was using it before, but I changed the theme, and then there was an error, so I changed it. Practical speaking.
2.QapTcha
Aiba is using it, it is simpler and more convenient.
3.Some Chinese Please!
A must-have for Chinese blogs.
4.Math Comment Spam Protection
Combined with Some Chinese Please!, the two swords work together to achieve great results.