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.
When I live I cry, If you don't kill me I'll die.
What English word retains the same pronunciation, even after you take away four of its five letters?
What goes through a door but never goes in. And never comes out?
What kind of pet always stays on the floor?
I have two eyes in the front and a lot of eyes on my tail
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?