Which of the following organisms has white blood?

The answer is B) Cockroach. The question is about the colour of blood, which in insects is really haemolymph. Insects have an open circulatory system, so their haemolymph bathes the organs directly and carries no respiratory pigment. In cockroaches it is colourless or whitish, which is the fact the examiner is testing.

• Lizard (A): Wrong. Reptiles have a closed circulatory system and red blood, because their red blood cells contain haemoglobin.
• House bug (C): This is ambiguous. If it means the bed bug (Cimex), it is also an insect with colourless haemolymph, so the question has a weak option here. Cockroach is the answer the paper expects.
• Mosquito (D): Wrong as the intended answer. Like other insects, its haemolymph is colourless, but the cockroach is the standard textbook example used for this fact.

The core concept is the difference between open and closed circulation and the pigments that carry oxygen. Mains often asks about this under comparative biology and adaptation, and it links to the classification of animals in the Environment and Ecology syllabus.

Trap: Assuming that every insect-like organism has red blood, or choosing the lizard because it is a vertebrate with blood in the everyday sense.