Google Indexing Wrong Webpages

This is a bit theoretical question, how you won't mind.

I have a website on which a user can ask a question & also answer it. But if the user is not logged in & he/she try to answer question then they will be redirected to the login page.

Now, suppose there are 10 questions on website, then there will be 10 individual links where user can visit & answer every question BUT if they are not logged in then those urls will become 10 individual login urls because of redirect.

That is what happened to me, Google has indexed all the answer page urls as login urls. Please see the image.

Google search image

I don't want google to index those urls which are redirecting users to login page. How can we prevent their indexing?