Yes. At least I cannot think of something more rational. But you know, I tried to find unique solutions several times and what I have noticed - it is not very simple to find impressing ones. They are all more or less similar
I also thought so and that's why I conducted researches. Basically, the most advanced and attractive solution I have found is hCaptcha. hCaptcha is designed to solve the most labor intensive problem in machine learning: labeling massive amounts of data in a timely, affordable, and reliable way. hCaptcha allows websites to make money serving this demand while blocking bots and other forms of abuse.