The correct answer to the question is option 'A' - In the head region.

Explanation:

Cockroaches are insects that belong to the class Insecta and the order Blattodea. They have a unique body structure consisting of three main regions - the head, thorax, and abdomen.

- The head region of a cockroach is where the completely developed endoskeleton and exoskeleton are present.

- The endoskeleton refers to the internal skeleton of the cockroach, which provides support and protection to the internal organs. It is made up of a series of interconnected plates called sclerites, which are composed of chitin, a tough and flexible substance. The endoskeleton in the head region helps in protecting the delicate sensory organs, such as the eyes, antennae, and mouthparts.

- The exoskeleton, on the other hand, refers to the outer covering of the cockroach's body. It is made up of a tough and rigid substance called cuticle, which is also composed of chitin. The exoskeleton acts as a protective covering, providing support and preventing the entry of harmful substances. In the head region, the exoskeleton covers the head capsule, which houses the sensory organs and mouthparts of the cockroach.

- The head region of a cockroach also contains various appendages, such as the antennae, compound eyes, and mouthparts. These structures are essential for the cockroach's sensory perception, feeding, and communication.

- In contrast, the thoracic region of a cockroach is primarily responsible for locomotion. It contains three pairs of jointed legs and two pairs of wings in some species. The abdominal region is mainly involved in digestion, reproduction, and excretion.

In conclusion, the completely developed endoskeleton and exoskeleton are present in the head region of a cockroach. This region contains the protective head capsule, sensory organs, and mouthparts.