Why is this the answer?

The answer is key because this clever little riddle is telling us a secret story about how a key works with a lock to keep things safe. A key is a very important, small tool, usually made of metal, that helps you control a door or a treasure box. It is like a tiny, magical helper that only does what you ask it to do. Let's look closely at the first clue, "I turn around once. What is out will not get in." When you use a key, you put it into the little hole on the door, which is called the keyhole. You grab the head of the key and turn it with your fingers. When you turn it one time, the lock snaps shut. This means the door is now locked, so people or animals who are *out* in the world cannot come *in* to your house or room. The key's first turn has created a strong, invisible shield to protect what is inside. Now for the next part of the riddle: "I turn around again. What is in will not get out." A lock does not just keep people out; it can also keep things in. If you lock a treasure chest or a special cupboard, you do not want the things inside to get out or be taken. When you turn the key a second time, you might be unlocking the door to let yourself in, or you might be locking it from the inside so that anything inside stays right where it is. To lock a door, you simply turn the key, and you control the entrance. The key is the only thing that makes the lock turn to keep things secure. The simple, turning action of the key is what controls the door and makes sure nothing leaves or enters without your permission. That is why this helpful and powerful little object, the key, solves the puzzle.