Zero Escape: Zero Time Dilemma

After the control room puzzle for C team, you have to pick the locker with the oxygen mask in it. It appears to be random. There are 10 lockers. You pick one, then 8 more empty lockers will open, and you have to decide whether to switch to the other remaining closed locker, or stick with your first choice. I guess that as you are more than likely to pick an empty locker for your first choice, switching your choice to the other locker has the best odds of picking the winner.

Even so, if you are unlucky enough to get it wrong, you can always use the flow charts and pick again later on, so it's not a missable trophy.