The hand, the eyes, and the brain work together to make human beings different from other animals. No other animals have all three parts to work together. No animals can do what human beings can do. Humans can do many things and feel many things with the hand. The hand can hold onto things and make things because the thumb  works with the fingers. This fifth finger is strong. Most animals don't have thumbs. The thumb can press against the other fingers. Without a thumb to press against the fingers, it is difficult to hold onto anything. The thumb and fingers can also fit the flat surface of a box and the curved   surface of a pencil. We can feel that something is hot or cold, soft or hard, smooth or rough. The hand, with thumb and fingers, is one of the best tools we have. Most animals see a flat picture. Their eyes can only see how high and how wide something is. Some animals see a different picture with each eye. Some don't see in colour. Humans see one picture with both eyes working together. We can see how high and how wide something is. We can also see how far in front of or in back of something a thing is. The brain tells other parts of the body how to work. Some of the things the body does are _ ; that is, we don't have to think about them. For example, we don't have to think to make our heart beat or our stomach work. The brain tells the eyes and hands how to make useful and beautiful things. That is how human beings become tool makers and artists. That is how human can have richer and better lives than other animals. According to the passage, when you say you hold onto something, you mean  _
you have it in your hand and keep it there by putting your fingers firmly roundit you have it in your arms and keep it there by putting your fingers firmly roundit you feel it with your hands you press the fingers of your right hand against those of your left hand