If you don't know how that kind of thing works, you are likely to make mistakes regarding it. If you know how it works, you can prevent yourself from making mistakes that could endanger yourself and/or others.
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4. a pharmacy store selling unapproved drugs I think
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the first answer is correct, but you could also say "all of the above"
Probably. If things get worse, you should check a doctor
yes they can because it messes with their brain and the way of thinking.
