in which of the following the notochord is present in embryonic stage

Options

A. All chordates
B. some chordates
C. Vertebrates
D. Non-chordates

Explanation

To solve the question regarding the presence of notochord in the embryonic stage, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding Notochord**:
- The notochord is a flexible rod-like structure that is present in the embryonic stage of chordates. It serves as a primary skeletal element in the early development of these organisms.

2. **Identifying Chordates**:
- Chordates are a diverse group of animals that include three main subphyla:
- **Urochordata (or Tunicata)**: In this group, the notochord is present only in the larval stage.
- **Cephalochordata**: Here, the notochord is present throughout the entire life of the organism.
- **Vertebrata**: In vertebrates, the notochord is present during the embryonic stage but is replaced by the vertebral column in adults.

3. **Analyzing the Options**:
- **Option 1: All Chordates**: This option suggests that the notochord is present in the embryonic stage of all chordates. This is true as all chordates exhibit a notochord at some stage of their development.
- **Option 2: Some Chordates**: This option implies that only a few chordates have a notochord in the embryonic stage, which is incorrect since all chordates do have it.
- **Option 3: Vertebrates**: While vertebrates do have a notochord in the embryonic stage, this option is misleading because it excludes other chordates that also possess a notochord.
- **Option 4: Non-Chordates**: Non-chordates do not have a notochord at any stage, making this option incorrect.

4. **Conclusion**:
- The correct answer is **Option 1: All Chordates**, as the notochord is indeed present in the embryonic stage of all chordates.

### Final Answer:
The notochord is present in the embryonic stage of **all chordates**.