a more beautiful girl - the most beautiful girl;
more interesting books -> most interesting books;
more beautiful trees -> most beautiful trees;
a good son -> a better son -> the best son;
a bad boy -> a worse boy -> the worst son;
bad food -> worse food -> worst food;
a more beautiful girl - the most beautiful girl;
more interesting books -> most interesting books;
more beautiful trees -> most beautiful trees;
a good son -> a better son -> the best son;
a bad boy -> a worse boy -> the worst son;
bad food -> worse food -> worst food;