The wind blew too hard for them.
It became too warm for them.
No one knows for sure.
A meteorite destroyed the Earth
There were huge earthquakes
There was a McDonalds on the corner
There were people on earth
None of the above
A volcano erupted blocking out the sun.
There was a space invasion.
A meteorite hit earth and added soot to the air.
A giant dinosaur ate them and is now hiding.
Some kinds of plants died, too.
No other living things were around.
The climate didn't change at all.
The atmosphere of the Earth became too warm.
Not enough air
Not enough water
Not enough food
All of the above
A rain storm
An extinct animal
Here's an interesting quiz for you.