In which of the following group notochord present in whole life?

Options

A. Hemichordata
B. Urochordata
C. Cephalochordata
D. Vertebrata

Answer

To determine in which group the notochord is present throughout the whole life, we can analyze each option provided:

1. **Hemicordata**: In this group, the notochord is not present throughout the organism's life. Instead, it is replaced during development. Therefore, this option is incorrect.

2. **Urochordata**: In this group, the notochord is present only in the larval stage. In the adult stage, the notochord is absent. Thus, this option is also incorrect.

3. **Cephalochordata**: This group is characterized by the presence of a notochord that persists throughout the entire life of the organism. Therefore, this option is correct.

4. **Vertebrata**: In vertebrates, the notochord is present during the early stages of development but is replaced by the vertebral column in adults. Hence, this option is incorrect.

Based on the analysis, the correct answer is **Cephalochordata**, as they possess a notochord throughout their entire life.

### Summary of Steps:
1. Analyze the presence of notochord in Hemicordata - **Incorrect**
2. Analyze the presence of notochord in Urochordata - **Incorrect**
3. Analyze the presence of notochord in Cephalochordata - **Correct**
4. Analyze the presence of notochord in Vertebrata - **Incorrect**