Explanation: Primary circular reactions according to Piaget involve activities which makes the infant focused on its own body, while secondary circular reactions involve activities where the infant's actions relate to the outside world, and are both enjoyable, and repeated.
Hair and nails are mostly made of protein. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood.
