Beak is formed by

The correct option is Jaws.

A beak, also known as a bill, is an external anatomical structure of birds which is also found in some other animals such as turtles, tortoises, and dinosaurs. In birds, the beak is formed by the elongation of the upper and lower jaws (the maxilla and mandible). These bony jaws are covered by a lightweight, keratinized sheath called the rhamphotheca, which gives the beak its hard, protective outer layer. Since modern birds do not have cheeks or teeth, their jaws have evolved to form the beak to assist in feeding, preening, defense, and other daily activities.