If you want to make a clean install of the new OS X Mavericks or even the older versions of Mac OS X, than I strongly suggest you to create a bootable OS X key or a drive.
Chemistry is the science that studies the composition, structure and properties of matter and the changes that occur during chemical reactions. Answer a few questions to see how good you really are in Chemistry?
You don't need an open fire to roast chestnuts, you can roast them in a comfort of your own home over a kitchen hob and they will end up just as delicious.
You probably heard about the alleged end of the world that could occur on December 21 2012 and about Mayan calendar predicting the apocalyptic events. Where did all this come from?