The kidney of frog are

Options

A. holonephros
B. mesonephros
C. metanephros
D. pronephros

Answer

### Step-by-Step Solution:

1. **Identify the Function of the Kidney in Frogs**:
- The kidneys in frogs serve as excretory organs, similar to their function in humans.

2. **Understand the Types of Kidneys**:
- There are four types of kidneys mentioned: holonephros, mesonephros, metanephros, and pronephros. Each type is associated with different groups of animals and developmental stages.

3. **Determine the Type of Kidney in Frogs**:
- The correct type of kidney for frogs is mesonephros. This is because frogs, being amphibians, possess mesonephric kidneys which are formed from the extended opisthonephros.

4. **Explain the Formation of Mesonephros**:
- The mesonephros is formed from the extended opisthonephros and includes tubules from the posterior nephric ridge.

5. **Relate to Other Organisms**:
- Mesonephros is commonly found in most fishes and amphibians, which further supports the classification of frogs as having mesonephric kidneys.

6. **Conclude with the Correct Answer**:
- Therefore, the correct answer to the question "The kidney of frog are" is option 2: mesonephros.