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How can I select buttons with just the keyboard?
I have been using OS X for only a while now and am finding certain things a bit hard to do. Consider an option box shown below :-

Pressing an enter key would shut down the system, however how do I select the "restart" or the "cancel" options using they keyboard alone? Whats the keyboard shortcut for that? Arrow keys just dont work. Coming from a Linux/Windows background, this is really confusing.