Answer:
What has words but never speaks?
Taken from a mine and then locked up in a wooden case. I am used by students everyday.
I cannot be burned in fire or drowned in water
I make you weak at the worst of all times. I keep you safe I keep you fine. I make your hands sweat and your heart grow cold. I visit the weak but seldom the bold.
I am a desire to munch
No matter how little or how much you use me, you change me every month.
What am I?
Animal
Difficult
Easy
Food
Funny
Kids
Logic