Why is this the answer?

The answer is breath because this super clever riddle is playing a fun trick with the word "hold." When you hear the first part, "As light as a feather," you might picture something that weighs almost nothing, like a fluffy little bird feather or a tiny piece of cotton floating in the air. That is exactly right for your breath! Your breath is just air moving in and out of your body, and air is so light that you never even notice its weight. You take deep breaths when you play outside and smaller breaths when you are sleeping, and the air always feels like it weighs zero. This part of the riddle describes what your breath is made of, which is light, invisible air. Now let us look closely at the second part of the riddle: "but you can not hold it for ten minutes." This is the really tricky part! The riddle is not asking you to hold your breath in your hands, like holding a ball or a toy. It is asking you to stop the process of breathing and keep the air that is already inside your body there, which is what we call "holding your breath." If you try to hold your breath, you can only do it for a little while. Maybe you can hold it for 30 seconds, or a minute if you are very good at swimming underwater, but you simply cannot hold it for ten whole minutes! No person is strong enough to do that, not even the biggest grown-up or a movie superhero. Why is this impossible? Because your amazing body needs air, which has important oxygen, every single second to keep your heart beating and your brain thinking. This is the most important job your body has! If you try to stop breathing for a long time, your body will take over and make you breathe again automatically. Because your breath is so light but you cannot physically stop the action of breathing for long, it is the perfect answer to this great riddle!