Answer:
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
I do not breathe, but I run and jump. I do not eat, but I swim and stretch. I do not drink, but I sleep and stand. I do not think, but I grow and play. I do not see, but you see me everyday.
What is often returned, but never borrowed/
Come up and let us go. Go down and here we stay.
In your fire you hear me scream, creaking and whining, yet I am dead before you lay me in your hearth.
Why was the cook arrested?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?