How will human beings become extinct?

Recently Dr Stephen Hawking asked the people of Yahoo! Answers "How can the human race survive the next hundred years?" Answers range from the absurd to the hopeful and to the simple reply of humans not being able to survive the next hundred years. Dr Hawking himself said he has no answer to the question. Even the great Dr Hawking has no answer to that, I guess human beings are screwed then.

With that being the case, I'll assume that the human race will be extinct in a century's time, hence my question "How will human beings become extinct?" After some thought, I've narrowed down to the choices below.

1. A nuclear war begins, countries nuke each other. The lucky ones are killed by the initial nuclear blasts, the not so lucky ones die eventually of radiation exposure.


2. A stray meteorite hits Earth. Once again, the lucky ones are killed by the initial impact, the ones that never kena Toto freeze to death because excessive dust in the atmosphere blocks the sun's ray causing a climate change that humans cannot control. Bruce Willis does not save the world by detonating the meteor.


3. Global warming becomes uncontrollable (might already have happened), the earth becomes hotter and hotter, eventually humans can't cope with the temperature and start dropping like flies. The Arabs out live the rest of the world but still die eventually. David Blaine survives the heat but dies of old age.


4. An epidemic spreads like wild fire. With all the world's funds put into developing weapons of destruction and rewarding people who provide information on Al Qeada's latest number 2 in command, no cure can be found. Human race dies a slow and painful death eventually.


5. The Vogons zap Earth into oblivion in order to build an inter-galactical highway. Just like in The Hitchhiker's Guide to the Galaxy. All life-forms on Earth are wiped away in an instant. The leaders of the world were still trying to agree on a ceasefire for the 100 year old Israel-Lebanon invasion.


6. We all die of George Bush's stupidity.

My heart tells me its option 6 but my brain tells me its option 3. What do you think? And are there any other possible answers?