Which of the following is true for all amphibians ?

Options

A. All have tail
B. Excretion by kidneys
C. Alimentry canal and urinary and reproductive tracts open into different chambers to the exterior
D. Heart is three -chambered with two ventricles

Answer

To determine which statement is true for all amphibians, let's analyze each option step by step.

### Step 1: Analyze the first statement - "All have tails."
- **Explanation**: Not all amphibians have tails. While many larval forms (like tadpoles) do have tails, adult amphibians (like frogs) typically lose their tails during metamorphosis.
- **Conclusion**: This statement is false for all amphibians.

### Step 2: Analyze the second statement - "Excretion by kidneys."
- **Explanation**: Amphibians do excrete waste products primarily through their kidneys. This is a characteristic feature of amphibians, as they have developed kidneys that function in the excretion of nitrogenous wastes.
- **Conclusion**: This statement is true for all amphibians.

### Step 3: Analyze the third statement - "Elementary canal and urinary and reproductive are open into different nodes."
- **Explanation**: In amphibians, the digestive, urinary, and reproductive systems open into a common cloaca, not separate openings. This means that this statement is incorrect.
- **Conclusion**: This statement is false for all amphibians.

### Step 4: Analyze the fourth statement - "Heart is three-chambered with two ventricles."
- **Explanation**: The heart of amphibians is indeed three-chambered, but it consists of two atria and one ventricle, not two ventricles. Therefore, this statement is also incorrect.
- **Conclusion**: This statement is false for all amphibians.

### Final Conclusion:
The only statement that is true for all amphibians is that they excrete waste through their kidneys. Therefore, the correct answer is option B: "Excretion by kidneys."

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