Registration questionnaire to prevent spammers

I want to add some specific General Knowledge question related to users of my targeted area 开发者_运维问答only at the user registration form because of spamming from untargeted users( from across world).

Is there any module I can use to add question/answer in the registration form?

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I would suggest using the CAPTCHA/reCAPTCHA and the CAPTCHA Riddler if you are looking for this exact use case. With these modules you can choose which forms to display CAPTCHA on and you can create your own custom questions and answers.

Otherwise, like Rimian says, there's Mollom

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Is it necessary for the question to be "General Knowledge"? You only want to determine if the user is human, right? I would use mollom:

http://mollom.com/
http://drupal.org/project/mollom

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If I were to do this, I would create a small module using hook_form_alter working on the registration form, which would add fields for the questions, as well as a verification function to check whether the answers were correct.