Crocodile and penguin are similar to whale and dog fish in which one of the following features?

Options

A. Possess a solid single stranded central nervous system
B. Lay eggs and guard them till they hatch
C. Possess bony skeleton.
D. Have gill slits at some stage.

Answer

To solve the question regarding the similarities between crocodiles and penguins with whales and dogfish, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Animals**: Recognize that crocodiles, penguins, whales, and dogfish are all part of the phylum Chordata. This is important as it indicates they share certain fundamental characteristics.

2. **Understand Key Characteristics of Chordates**: Chordates are defined by specific features at some stage in their life cycle. One of the most significant characteristics is the presence of gill slits (also known as pharyngeal clefts) during embryonic development.

3. **Analyze the Options**: The question provides several features to compare. We need to evaluate each option to see which one applies to all four animals:
- **Option 1**: Solid single-stranded nervous system - Incorrect, as chordates have a hollow nerve cord.
- **Option 2**: Lays eggs and guards them - Incorrect, as not all of these animals exhibit this behavior.
- **Option 3**: Possesses a bony skeleton - Incorrect, as dogfish have a cartilaginous skeleton.
- **Option 4**: Presence of gill slits at some stage - Correct, as all these animals have gill slits during their embryonic development.

4. **Conclusion**: The correct answer is that crocodiles and penguins are similar to whales and dogfish in that they all possess gill slits at some stage of their life cycle.

### Final Answer:
Crocodile and penguin are similar to whale and dogfish in that they all possess gill slits at some stage of their life cycle.

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