Answer:
I have a straight back and sharp teeth to cut objects.
You throw me out when you use me and take me in when you are done.
I transfer oxygen from the atmosphere to your blood
The more you work, the more I'll eat.You keep me full, I'll keep you neat. What am I?
You heard me before and then again. Afterward I die until you call me again.
Whatโs a carpetโs favorite sport?