True, sleep problems indeed are a quite often occurence among children as well as adults - they do occur quite often but don't necessarily occur all the time for people to whom it does happen. At the same time, when someone suffers from sleep problems, this doesn't necessarily mean that he cannot sleep at all.
It occur when plaque and bacteria is not adequately removed from the surface of the tooth
If this left untreated , it will create holes in your teeth which eventually make it more prone to destruction
I am not sure, but I think the answer is c.
The earths water supply is not affected from water pollution
