The amphibians are characterized by :-

Options

A. Only aquatic habit
B. Monocondylar skull
C. Scaleless, smooth moist and glandular skin
D. Claws present at the tip of digits

Answer

To answer the question "The amphibians are characterized by:", we will analyze the characteristics of amphibians step by step.

### Step-by-Step Solution:

1. **Habitat**: Amphibians are primarily found in various habitats, including terrestrial (land), fossorial (burrowing), arboreal (tree-dwelling), and freshwater aquatic ecosystems. This diversity in habitat is a key characteristic of amphibians.

**Hint**: Think about the environments where amphibians thrive and how they adapt to different habitats.

2. **Skull Structure**: Amphibians possess a dicondylar skull, which is a significant anatomical feature. This means that they have two condyles (rounded ends of the bone) at the base of their skull that articulate with the vertebrae.

**Hint**: Recall the difference between monocondylar and dicondylar skulls and which one is associated with amphibians.

3. **Skin Characteristics**: The skin of amphibians is smooth, moist, and often permeable. This characteristic is crucial for their respiration and hydration, as many amphibians can absorb water and gases through their skin.

**Hint**: Consider the importance of skin texture and moisture for amphibians in relation to their respiratory needs.

4. **Limbs and Claws**: Amphibians typically do not have claws at the tips of their digits (fingers and toes). Instead, they have webbed feet or flattened toes that aid in swimming and movement through their environments.

**Hint**: Think about the adaptations amphibians have for locomotion in both water and land.

### Conclusion:
Based on the analysis, the correct characterization of amphibians includes their diverse habitats, dicondylar skull structure, smooth and moist skin, and the absence of claws at the tips of their digits.

### Final Answer:
Amphibians are characterized by their diverse habitats, dicondylar skull, smooth and moist skin, and lack of claws.