All of the following characterised amphibians except they:

Options

A. are usually tetrapods
B. undergo metamorphosis
C. have a 3-chambered heart
D. have gills in an adult

Explanation

To solve the question "All of the following characterized amphibians except they:", we need to analyze the characteristics of amphibians and identify which statement does not apply to them.

### Step-by-Step Solution:

1. **Identify Characteristics of Amphibians**:
- Amphibians are known for having four limbs, which classifies them as tetrapods. This characteristic is true for all amphibians.

2. **Metamorphosis**:
- Amphibians undergo a process called metamorphosis, which includes stages such as egg, larva (tadpole), and adult. This is a defining characteristic of amphibians, and all of them exhibit this life cycle.

3. **Heart Structure**:
- The heart of amphibians is typically three-chambered, consisting of two atria and one ventricle. This is another true characteristic of amphibians.

4. **Gills in Adult Stage**:
- The statement that amphibians have gills in their adult stage is incorrect. While amphibians may have gills during their larval stage (like tadpoles), they typically lose these gills and develop lungs as adults.

5. **Conclusion**:
- Based on the analysis, the statement that amphibians have gills in the adult stage is the one that does not characterize amphibians. Therefore, the correct answer is the option that states this incorrect characteristic.

### Final Answer:
The correct answer is that amphibians do not have gills in the adult stage.