In which of the following organisms the regulation of blood flow cannot be precisely regulated?

Options

A. Pheretima
B. Mosquito
C. Labeo
D. Cuttlefish

Answer

To determine which organism has a circulatory system that cannot precisely regulate blood flow, we need to analyze the circulatory systems of the given organisms:

1. **Earthworm (Ferritima)**: Earthworms have a closed circulatory system. This means that blood is contained within vessels, allowing for precise regulation of blood flow. Therefore, earthworms can regulate blood flow effectively.

2. **Mosquito**: Mosquitoes, being insects, possess an open circulatory system. In an open circulatory system, blood (hemolymph) is not confined to vessels but instead bathes the organs directly. This lack of a defined system means that blood flow cannot be precisely regulated. Hence, mosquitoes do not have a well-organized way of circulating blood.

3. **Labeo (a type of fish)**: Labeo, like other fish, has a closed circulatory system. This system includes a heart, arteries, veins, and capillaries, allowing for precise regulation of blood flow. Therefore, Labeo can effectively regulate blood circulation.

4. **Cuttlefish**: Cuttlefish also belong to the group of cephalopods, which have a closed circulatory system. Similar to fish, they possess a well-defined circulatory system that allows for precise regulation of blood flow.

After analyzing the circulatory systems of the organisms, we conclude that the organism in which blood flow cannot be precisely regulated is the **Mosquito**.

### Final Answer: Mosquito