I give you a group of three. One is sitting down, and will never get up. The second eats as much as is given to him, yet is always hungry. The third goes away and never returns. What are the three things?
I make ash, but I’m not a bonfire.
I can expel rocks, but I’m not a slingshot.
I can be a mountain, but I’m not in the Himalayas.
I have a crater, but I’m not the Moon.
I erupt, but I don't have a bad temper.
What am I?
It is energy and motion, it can fly across the ocean.
It can listen and even speak, it can see and even seek.
It eats neither fruit nor gruel, it eats energy and fuel.
Better say: It doesn't eat; It is transformed into heat.
What is it?