The correct answer is option 'D', which states that oxygen reaches tissues directly through diffusion.

Explanation:

1. Overview of the respiratory system:
The respiratory system is responsible for the exchange of gases, specifically oxygen and carbon dioxide, between the external environment and the body's cells. In most animals, including insects like cockroaches, this process involves the use of a respiratory pigment to transport oxygen.

2. Role of respiratory pigments:
Respiratory pigments are specialized molecules found in the blood or tissues of many animals. These pigments bind to and transport oxygen, increasing the efficiency of oxygen transport throughout the body. Hemoglobin is the respiratory pigment found in vertebrates, while insects utilize different pigments such as hemocyanin or hemerythrin.

3. Blood of Cockroach:
The blood of a cockroach, known as hemolymph, does not contain respiratory pigments. Hemolymph is a fluid that circulates throughout the body cavity of insects and performs various functions, including nutrient transport and waste removal. However, it does not have a specialized pigment for oxygen transport.

4. Respiratory system of Cockroach:
Cockroaches have a unique respiratory system that does not involve the use of respiratory pigments. Instead, they rely on a network of tiny tubes called tracheae, which are connected to the external environment through small openings called spiracles. Oxygen enters the cockroach's body through these spiracles and diffuses directly into the tissues.

5. Diffusion of Oxygen:
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the case of oxygen, it moves from an area of higher concentration (external environment) to an area of lower concentration (tissues) through passive diffusion. This process does not require the presence of a respiratory pigment.

6. Intracellular Capillary System:
Option 'C' mentions that oxygen goes to tissues by the intracellular capillary system. However, this is not accurate for cockroaches. Intracellular capillaries are characteristic of higher vertebrates and allow for efficient oxygen transport to tissues. In cockroaches, oxygen primarily reaches the tissues through direct diffusion.

In conclusion, the blood of a cockroach does not contain a respiratory pigment, and oxygen reaches the tissues directly through diffusion. This is due to the unique respiratory system of cockroaches, which utilizes tracheae and spiracles for gas exchange.

In cockroaches respiraton occurs through lateral pores(spiracles) through the process of diffusion.
so option d is correct.