What is absent in the blood of cockroaches?
A. Plasma
B. Respiratory Pigment
C. Nutrients
D. Blood cells

Hint: The cockroach's body is elongated, bilaterally symmetrical and dorsoventrally flattened. It has a chitinous exoskeleton. Hardened segments of exoskeleton are called sclerites. The blood vascular system of the cockroach is open type i.e it lacks blood vessels.

Complete answer:
To solve the given question we must be aware of the circulation in the heart.
 In Cockroaches the blood vessels flow through open spaces known as the lacunae of the sinuses present in the tissue. In them the blood vessels do not remain inside the blood vessels. The rate of blood circulation is very slow in Cockroaches.
The cockroaches’ blood is colourless and it has many white blood corpuscles.
The blood from the sinuses enters the heart through ostia. After the purification of blood, it is again passed into the sinus.
The visceral organs are present in the blood known as the haemolymph. This haemolymph has haemocytes.
The blood of the cockroach is colorless due to the absence of haemoglobin which is the respiratory pigment in blood. Therefore, its blood lacks respiratory pigment or haemoglobin.

Since now we are well aware of the circulation of blood in cockroaches therefore the correct answer to the question is respiratory pigment.

Note: Here it must be noted that the cockroach has thirteen chambered hearts. These chambers are of the shape of the funnels with ostia present on each side. Each chamber is divided into two parts. One of them is a narrow tubular anterior aorta and the other one is a posterior pulsating heart.