Hi arunrnair,
You've described a legitimate concern for Test Takers who review lots of questions in these Forums - the more questions you see, the more likely that you'll run into questions that you'll face on your practice CATs. Seeing questions on a CAT that you've already answered will make those CAT results inaccurate. As such, you might want to invest in some GMAT resources (Courses, books, etc.) that will allow you to practice and use this Forum as more of a 'support' resource.
Have you taken any FULL-LENGTH practice CATs yet? If so, then how did you score?
If you have not taken any yet, then you can download 2 for free from
www.mba.com. A FULL CAT takes about 4 hours to complete, so make sure that you've set aside enough time to do so in one sitting.
I have a few other questions too:
1) What resources are you using to study with?
2) When are you planning to take your GMAT?
3) What is your goal score?
GMAT assassins aren't born, they're made,
Rich