The theory that the threat of nuclear war is enough to prevent an attack is called: Nuclear deterrent
The theory is based on the likelihood that every nations would fear a mutual destruction when initiating attack to countries that own nuclear weapon. Even if a country emerge victorious from a nuclear war, the damage that caused by opposition's nuclear would damage the environment of the victors for decades.
Answer: Hi!
PIN stands for personal identification number. They are used to confirm your identity, because every set of numbers is unique to the person.
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Because we let anyone with money into the system and they elect other people with money. pretty much its because of money