Good Riddles

Question: how do cows count?

Question: I attach to your hip and I sing all day.
All I want to do is play.

Question: It breaks away from its pack. It creates holes in its victims. It can travel for miles and then disappear. It is part of a dying breed. What is it?

Question: It's got twists and turns, but has no curves.
Twist it to fix it, turn it to ruin it.

What is it?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?