Answer:
What word is a plural, but when you add an "S" to the end, it becomes singular?
What is lengthened by being cut at both ends?
I am black when I am clean and white when I am dirty?
My teeth are sharp, my back is straight, to cut things up it is my fate.
What letter comes next: O T T F F S S ?
I am owned by Old McDonald.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?