Why is this the answer?

The answer is eye because this clever riddle uses fun word pictures to describe your eye, which is one of the most important parts of your body and helps you see the world. Let us look closely at the first clue: "A hole in a pole". This part is a little tricky, so let us break it down. Think about the very center of your eye. There is a tiny black circle called the pupil. That pupil is the "hole" that lets light in so you can see. The pupil changes size, getting smaller in bright sunshine and bigger when it is dark. The colorful part that surrounds the pupil is called the iris. The riddle uses the word "pole" which can mean a long, thin stick, but it also just means a center or a focus point. You can think of the long, round shape of your eye and the way the pupil sits inside the colorful iris as the center or the "pole" of your sight. The next clue is, "though I fill a hole in white." This is a wonderful picture. Now, look at the white part all around your iris. The whole, rounded eyeball sits neatly inside a bony space in your skull called the socket. The dark part, with the iris and pupil, is right in the middle of all that white, like a dark circle filling up a hole in a white field. Your eye itself is filling up the empty hole in your head where you see from, and all the white shows around it. It is a very clever way of describing the parts of your eye without ever saying the real names. Finally, the riddle says, "I'm used more by the day, and less by the night." This is the easiest clue to solve. When the sun is shining brightly, your eyes are wide open and working hard all the time. They are helping you read, play games, and find your friends and toys. That is why they are "used more by the day." But when it gets dark and it is time for you to go to bed, you close your eyes and they get a long rest so they can be ready for the next morning. They are "less by the night" because they are sleeping just like you are. The eye perfectly matches all three clever parts of this fun word puzzle. It is amazing how such a simple, small part of your body can do such important work.