You have to pick:

I have the "Zombie Survival Guide", so I will survive the apocalypse.

Despite what the movies say I suspect that a zombie outbreak's death rate would be less than 1/3, so overall my chances are better with that.

I suspect that something that kills less than 1/3 of a city's population wouldn't warrant the name "apocalypse", though. And even if the proportion were that small it would still result in a greater total number of deaths, many of which will be quite horrific and awful. So I think it's still a hard choice and I'm leaning toward the one that's guaranteed to only kill 7 people.

1/3 of 20 is 6.6666..., so I'll assume that rounds up to 7.

But zombie apocalypes are loads of fun.

But lots and lots of people dying in fear and agony _isn't_ fun. And many of the dead will be people you know personally, too.

the worst is when your family members try to eat you!

@bryan.dersken: Yep, 7 are going to die