In which of the following animal neural system started ?

Options

A. Hydra
B. Amoeba
C. Cockroach
D. Earthworm

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which animal is considered to have the first neural system. We need to evaluate the options provided to determine the correct answer.

2. **Evaluating the Options**:
- **Option 1: Hydra**: Hydra is a simple organism that possesses a primitive neural system known as a nerve net. This network of neurons is distributed throughout its body and allows for basic responses to stimuli.
- **Option 2: Amoeba**: Amoeba is a unicellular organism and does not have a nervous system. Therefore, this option is incorrect.
- **Option 3: Cockroach**: Cockroaches have a more complex nervous system with segmented ganglia, but they are not the first to develop a neural system. Thus, this option is also incorrect.
- **Option 4: Earthworm**: Earthworms have a more developed nervous system than Hydra, but they are not the first to have a neural system. Hence, this option is incorrect as well.

3. **Conclusion**: Based on the evaluation, the correct answer is **Option 1: Hydra**, as it is the organism where the neural system is believed to have first started.

### Final Answer:
The neural system started in **Hydra**.