XF 1.5 Q&A Captcha For Social Accounts Signup ?

[Juste_me__]

I am trying to have Q&A Captcha displayed during the sign up page for users who opt to sign up using their Twitter | FB accounts. Basically, I am using Captcha not only to stop SPAM, but also to validate certain level of knowledge required by any user before being able to sign up. Hence, I am utilizing Q&A Captcha to place this technical question.

I was wondering if anybody has come a cross similar scenario or know what it takes to add Captcha for social accounts signup page ?

Thanks