O'Brien asks several very specific questions to determine the possible loyalty that Julia and Winston might have to a rebellion such as the alleged Brotherhood. They are these:

1. Are you prepared to give your lives? 

2. Are you prepared to commit murder? 

3. Are you prepared to sabotage other people?

4. Are you prepared to betray your country to foreign powers? 

5. Are you...

"prepared to cheat, to forge, to blackmail, to corrupt the minds of children, to distribute habit-forming drugs, to encourage prostitution, to disseminate venereal diseases -- to do anything which is likely to cause demoralization and weaken the power of the Party?"

6. Could you throw sulfuric acid in a child's face?

7. Are you willing to lose your identity?

8. Are you prepared to commit suicide?

To all of these questions the two answered "yes"...

9. Are you prepared, "the two of you, to separate and never see one another again?"

Julia said she could not do this... and eventually Winston did too.