In some reCaptchas (I assume this is somehow configurable), you only need to get one correct word (I'm not sure how close the second word should be).
I tested in reCaptcha on my own website and it worked (two words wrong = failure, one word on the right + one incorrect = success); tested in stackoverflow reCaptcha and it is not ... I had to get both words correctly. That is why I think it is customizable.
I found this post along with the one below (where I read that only one word should be right) precisely because it is too difficult for me to go through reCaptcha either; Too often you have to update more than 5 times to get an readable pair. Another message: Are reCAPTCHA CAPTCHA more complex or just me .
LFLFM
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