Of course option d is correct , same nematocyst can't be used again. one nematocyst can be used only one time...

The correct answer is option 'D': The same nematocyst cannot be used again and again.

Explanation:
Nematoblast cells, also known as cnidoblasts, are specialized cells found in the tentacles of Hydra, a freshwater polyp. These cells contain a specialized structure called a nematocyst, which is used by the Hydra for capturing prey and for defense against predators.

1. Nematocyst formation:
- Nematocysts are formed inside the nematoblast cells. These cells contain a coiled thread-like structure called the cnidocil, which is connected to a capsule called the cnidocyst.
- When a prey comes in contact with the cnidocil, it triggers the discharge of the nematocyst.
- The nematocyst rapidly everts and releases a harpoon-like structure containing toxins, which helps in paralyzing the prey.

2. Arise from interstitial cells:
- Nematoblast cells arise from interstitial cells, which are undifferentiated cells found in the epidermis of Hydra.
- Interstitial cells have the ability to differentiate into various cell types, including nematoblast cells.
- These cells undergo a process of maturation and become nematoblast cells, which are specialized for prey capture and defense.

3. Paralyzing the prey:
- Nematoblast cells and their nematocysts play a crucial role in paralyzing the prey.
- When a prey comes in contact with the cnidocil, the nematocyst is discharged, injecting toxins into the prey.
- These toxins help in immobilizing and paralyzing the prey, making it easier for the Hydra to capture and consume it.

4. The same nematocyst cannot be used again and again:
- Once a nematocyst is discharged, it cannot be reused. The discharged nematocyst is replaced by a new one inside the nematoblast cell.
- The process of nematocyst discharge is irreversible, and the nematoblast cell needs to synthesize and replace the discharged nematocyst for future use.

In conclusion, the statement that is wrong regarding nematoblast cells of Hydra is option 'D': The same nematocyst can be used again and again. Once a nematocyst is discharged, it cannot be reused and needs to be replaced by a new one.