Which one of the following groups of animals is correctly matched with its one characteristic feature without even a single exception?

Options

A. Chondrichthyes - Posses cartilaginous endoskeleton
B. Mammalia - give birth to young ones
C. Reptilia - Possess 3 - chambered heart with one incompletely divided ventricle
D. Chordata - possess a mouth provided with an upper and a lower jaw.

Answer

To determine which group of animals is correctly matched with its characteristic feature without any exceptions, we will analyze each option provided:

### Step 1: Analyze Option A - Chondrichthyes
- **Characteristic Feature**: Cartilaginous endoskeleton.
- **Analysis**: All members of the class Chondrichthyes, which includes sharks and rays, possess a cartilaginous endoskeleton. There are no exceptions to this feature.
- **Conclusion**: This option is correctly matched.

### Step 2: Analyze Option B - Mammalia
- **Characteristic Feature**: Give birth to young ones (viviparous).
- **Analysis**: While most mammals are viviparous, the platypus is an exception as it is oviparous (lays eggs).
- **Conclusion**: This option is not correctly matched due to the exception.

### Step 3: Analyze Option C - Reptilia
- **Characteristic Feature**: Possess a 3-chambered heart with 1 incompletely divided ventricle.
- **Analysis**: Most reptiles do have a 3-chambered heart, but crocodiles are an exception as they possess a 4-chambered heart.
- **Conclusion**: This option is not correctly matched due to the exception.

### Step 4: Analyze Option D - Chordates
- **Characteristic Feature**: Possess a mouth provided with an upper and lower jaw.
- **Analysis**: Not all chordates have a jaw. For instance, cyclostomes (like lampreys and hagfish) are jawless.
- **Conclusion**: This option is not correctly matched due to the exception.

### Final Conclusion
After analyzing all options, we find that:
- **Correct Answer**: Option A - Chondrichthyes with the characteristic feature of having a cartilaginous endoskeleton is the only group that is correctly matched without any exceptions.

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