Which of the following structures in molluscs, tests the chemical nature of water?

Options

A. Keber's organ
B. Osphradium
C. Pericardial gland
D. Organ of Bojanus

Answer

To solve the question "Which of the following structures in molluscs tests the chemical nature of water?", we can follow these steps:

### Step 1: Understand the question
We need to identify a specific structure in molluscs that is responsible for testing or sensing the chemical nature of water.

### Step 2: Recall the anatomy of molluscs
Molluscs belong to the phylum Mollusca, which is characterized by a body that is typically divided into three main parts: the head, the visceral mass (or hump), and the foot. They also have a mantle that covers the visceral mass.

### Step 3: Identify relevant structures
Within the anatomy of molluscs, we need to identify which structures are involved in sensing the environment, particularly the chemical composition of water.

### Step 4: Focus on chemoreceptive organs
Among the various structures, the osphradium is known to be a chemoreceptive organ found in the mantle cavity of molluscs. Its primary function is to test the chemical nature of water, allowing the mollusc to assess its environment.

### Step 5: Eliminate other options
The other options mentioned, such as the pericardial gland and caber's organ, are not primarily involved in testing the chemical nature of water. The pericardial gland is involved in excretion, and caber's organ is also an excretory organ.

### Conclusion
Based on the information gathered, the structure in molluscs that tests the chemical nature of water is the **osphradium**.

### Final Answer
The correct answer is **osphradium**.

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