The colonists fought to prevent any diminution of their rights by the king. This decrease of their rights seemed very unfair.
It means "belonging to them," as in "That is their dog."
It means that the person saying it wants to know the definition of what he is saying
Only one of these is a sentence: That's nice of you to say.It's nice of you to say so.If you know which is which, you have knowledge of sentences and non-sentences.