Similar to the q/v sections, you won't be allowed to move onto the next question without filling out each answer component. So the most you can do is randomly pick an answer before you can move onto the next.
If you run out of time, then the question will simply be marked as incorrect. You can get a few questions wrong on IR and still get a "perfect" score of 8/8. You can't just leave it blank when the time is still ticking.
For more information on integrated reasoning, please see: http://www.gmatpill.com/gmat-practice-t ... -reasoning
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