Why is this the answer?

The answer is breath because this clever little riddle plays a fun trick on your mind using the word "hold." When you first hear the riddle say "I'm light as a feather," it makes you picture something that weighs almost nothing, like a fluffy little bird feather or a tiny piece of cotton floating in the air. That part is absolutely true for your breath! Your breath is just air moving in and out of your body, and air is so light that you do not even notice you are moving it all day long. You take big breaths when you are running and quiet little breaths when you are sleeping, and it never feels heavy at all. Now, let us think about the trickiest part of the riddle: "yet the strongest man can't hold me for more than 5 minutes." This is where the fun word game happens! The word "hold" here does not mean picking something up with your hands, like holding a book or a toy. It means to hold your breath, or to stop the air from coming in and out of your body. Even the strongest person in the whole world, who can lift heavy things and run the fastest races, cannot keep their breath away from their lungs for long. Try holding your own breath for just a little while. What happens? Your body quickly sends a very important message to your brain that says, "I need to breathe again now!" You might start to feel a little uncomfortable or dizzy. That is because your body needs air every moment to get the special gas called oxygen, which keeps all your parts working. If a person tried to hold their breath for a whole five minutes, their brain would not get enough oxygen, and they would pass out. That is how important breathing is! The riddle is a smart way of reminding everyone, from a little kid to the strongest grownup, that breathing is the one thing we absolutely must do, and no amount of strength can stop it. Your breath is light and free, and your body will always make you let it go and bring more in.