Select all images below that match the one on the right.

I see following task in reCaptcha some times: Select all images below that match the one on the right. My clients ask me what does it mean. I don't know. Can anyone explain how to solve this kind of CAPTCHA task? Images look like completely unrelated. -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.