Assertion: Blood is colourless in the insects
Reason: Insect blood has no role in oxygen transport
A. Both assertion and reason are correct and the reason is the correct explanation for assertion
B. Both Assertion and Reason are correct but the reason is not the correct explanation for assertion
C. The assertion is correct but the reason is incorrect
D. Both assertion and reason are incorrect

Hint: Blood in insects is called hemolymph and is pale yellow or greenish because of the absence of respiratory pigments. Oxygen transport in blood mainly occurs by the process of diffusion and entry of oxygen and exit of carbon dioxide occur through the spiracles.

Complete answer:
Blood of insects is different from the blood of humans. In humans, the blood contains haemoglobin which gives the colour red to the blood and is also responsible for the transport of oxygen. Unlike humans, the blood of insects do not have haemoglobin and it does not transport gases. Insects have tubes and sacs that directly exchange gases between cells and the outer environment. Due to which, insect blood is pale yellow or green. Insects mostly have hemolymph. RBCs are absent in haemolymph and main components are amino acid acids, ions and carbohydrates. The colour of the hemolymph is pale yellow or green. Oxygen is mostly transported in insects through diffusion through little openings on their surface, but passive transport of oxygen can occur through haemolymph. Respiratory pigments are absent in haemolymph.
Hence, the correct answer is option (B).

Note: Cockroaches have an open circulatory system. Lungs are absent. They draw external air through an opening on their body called spiracles and the oxygen is transported to cells through tubes known as trachea by the process of diffusion. Diffusion is a process in which molecules flow from a higher concentration level to a lower concentration level.