The fluid that comes out of earthworm while piercing it (without damaging its gut) is

The correct option is coelomic fluid.

To understand why this is the correct answer, let's look at the anatomical structure of an earthworm:

1. Body Cavity (Coelom): Earthworms are coelomate animals, meaning they possess a true body cavity called the coelom. The coelom is located between the outer body wall and the inner alimentary canal (gut).
2. Coelomic Fluid: The coelom is filled with an alkaline, watery fluid known as coelomic fluid. This fluid contains water, salts, proteins, and various types of coelomocytes (cells that play a role in immunity and excretion). It acts as a hydrostatic skeleton, aiding in locomotion and maintaining the shape of the worm.
3. Piercing the Body Wall: If you pierce the body wall of an earthworm carefully without damaging its gut, you enter only the coelomic cavity. Because the gut is untouched, no digestive fluids are released. Instead, the fluid residing in the body cavity—the coelomic fluid—exudes from the puncture.

Let's briefly evaluate the other options:
- Slimy mucous: This is secreted by secretory cells in the outermost layer (epidermis) of the skin to keep the skin moist for respiration, not stored inside the body cavity.
- Excretory fluid: This fluid is processed and expelled through specialized structures called nephridia, rather than filling the main body cavity directly in large free-flowing quantities.
- Hemolymph: Earthworms have a closed circulatory system with blood vessels containing blood (with hemoglobin dissolved in plasma), rather than an open hemolymph system.

Therefore, the fluid that oozes out upon piercing the body wall without damaging the gut is the coelomic fluid.