Hi kml, I won't answer all of your questions because I'm in a hurry, but for your first question: It is an island of great beauty. If you used "the" in this sentence, it would imply that there was only ONE very beautiful island in the world, or that the people reading the sentence would know which island you meant. That doesn't make sense to most people, because most people believe that there are lots of beautiful islands in the world.
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