Which of the following is correctly stated as happens in the common cockroach?

Options

A. The food is ground by mandibles and gizzard
B. Malpighian tubules are excretory organ projecting out from the colon
C. Oxygen is transported by haemoglobin blood
D. Nitrogenous excretory product is urea

Answer

To determine which statement about the common cockroach is correctly stated, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Evaluate the First Statement**:
- The statement claims that food is ground by the mandible and gizzard.
- In cockroaches, the mandibles are indeed used to chew and break down food, and the gizzard further grinds the food into smaller particles.
- **Conclusion**: This statement is correct.

2. **Evaluate the Second Statement**:
- This statement suggests that Malpighian tubules are excretory organs that project out of the colon.
- However, in cockroaches, Malpighian tubules actually project from the midgut, not the colon.
- **Conclusion**: This statement is incorrect.

3. **Evaluate the Third Statement**:
- The statement indicates that oxygen is transported through hemoglobin in the blood.
- In cockroaches, the respiratory pigment is not hemoglobin but hemocyanin, which is responsible for oxygen transport.
- **Conclusion**: This statement is incorrect.

4. **Evaluate the Fourth Statement**:
- This statement claims that the nitrogenous excretory product is urea.
- In reality, cockroaches excrete ammonia as their nitrogenous waste, making them ammonotelic.
- **Conclusion**: This statement is incorrect.

### Final Conclusion:
After evaluating all the statements, the only correct statement regarding the common cockroach is the first one: "Food is ground by mandible and gizzard."