Answer:
Consuming food would be pretty tough without these chompers
There is one in every corner and two in every room.
What was the first man made invention that could see through a wall?
I shave several times a day, yet I still have a beard. Who am I?
What occurs four times in every week, twice in every month, only once in a year but never in a day?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.