Which one of the following simplest excretory organs ?

Options

A. Alveoli
B. Flame cells
C. Nephridia
D. Kidney

Answer

To determine the simplest excretory organ from the given options, we can follow these steps:

### Step 1: Understand the Options
The options provided are:
1. Alveoli
2. Plain cells
3. Nephridia
4. Kidney

### Step 2: Analyze Each Option
- **Alveoli**: These are tiny air sacs in the lungs involved in gas exchange, not excretion.
- **Plain cells**: This term is vague, but it generally refers to simple cells without specialized functions.
- **Nephridia**: These are excretory structures found in some invertebrates, such as annelids, but they are more complex than the simplest excretory organs.
- **Kidney**: This is a complex organ responsible for excretion in vertebrates, particularly in humans.

### Step 3: Identify the Simplest Excretory Organ
The simplest excretory organ is found in the simplest freshwater invertebrates, such as flatworms, rotifers, and nemertians. This organ is known as the **flame cell**.

### Step 4: Conclusion
Based on the analysis, the simplest excretory organ is not listed among the options, but if we consider the closest option related to simple organisms, it would be **plain cells**. However, the correct answer based on the context of the question would be flame cells, which are not explicitly listed.

### Final Answer
The simplest excretory organ is the **flame cell**.

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