Which of the following group of characters is present in all chordates in some or other stage in their life or Chordates differ from nonchordates in having

Options

A. Mammary glands, hairs, and gill silts
B. Notochord, gill silts ,and dorsal tubular nervous system
C. Notochord, scales, and dorsal tubular nervous system
D. Gill slits, vertebral column, and notochord

Answer

To answer the question regarding the group of characters present in all chordates at some stage in their life, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chordates**:
- Chordates are a diverse group of animals that share certain key characteristics at some point in their life cycle. These characteristics help distinguish them from non-chordates.

2. **Identifying Key Characteristics**:
- The main characteristics that define chordates include:
- **Notochord**: A flexible rod-like structure that provides support.
- **Dorsal Tubular Nerve Cord**: A nerve cord located along the back, which develops into the spinal cord in vertebrates.
- **Pharyngeal Gill Slits**: Openings in the throat area that can develop into gills in aquatic species or other structures in terrestrial species.
- **Post-anal Tail**: An extension of the body past the anal opening.

3. **Analyzing the Options**:
- **Option A**: Mammary glands, hairs, and glycids - These are characteristics of mammals specifically, not all chordates.
- **Option B**: Notochord, gill slits, and dorsal tubular nervous system - These are indeed present in all chordates at some stage.
- **Option C**: Notochord, scales, and dorsal tubular nervous system - Scales are not a characteristic of all chordates.
- **Option D**: Gill slits and notochord - This option is incomplete as it does not mention the dorsal tubular nervous system.

4. **Selecting the Correct Answer**:
- Based on the analysis, Option B (Notochord, gill slits, and dorsal tubular nervous system) is the correct answer as it includes the essential characteristics that are present in all chordates at some stage of their life.

### Final Answer:
**Option B: Notochord, gill slits, and dorsal tubular nervous system.**

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