I would like to answer those:
RADIOACTIVE DECAY: Yes, there are many forms of radioactive decay. However, radioactive elements (e.g. Uranium) go through a decay "chain", which is a series of decays of the various sorts to effectively turn themselves into a more stable element. They effectively become many different elements during this time, but eventually they want to end up as iron, which has the most stable structure energy-wise. This is a main reason why many planets have iron cores. This is from nuclear physics; perhaps it's a bit too specialized for a quiz question
BRAIN USAGE: All of the theories and stigma behind us using only 10% of our brains and the rest is untapped potential is dead wrong, plain and simple. The main confusion may be that we only use about 10% of our brains for CONSCIOUS ACTIVE THOUGHT, i.e. our primary senses, the decision and action to move to a particular location or to pick up something, etc. The remaining 90% is not unused matter; it is used for SUBCONSIOUS thought and automated process such as regulating heartbeat, body healing, digestion, memory storage, etc. You ask any legitimate doctor or psychologist about this and they will tell you exactly what I have.
BREATHING: First point, I did not specifically say "brain" cells; I said cells in general. Second, yes people can be revived after not having air for longer than 5 minutes; but if they have not been able to breath for at least five minutes, some cells all over their body will have died. This is a medical fact. The human body can still recuperate from this if not too many cells have died within the important organs, and I honestly don't know how long someone can go without air before they have no chance for revival. But that is not the question I asked
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