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 they?
Im probably way off on these.
The second:a black hole. Any amount of matter can be thrown at a black hole and it will still suck up more
The third:the past. Events in the past have come and gone and will never return, only get further away.